IPv6 issues with trusted proxies

There's been a lot of fail reports from CPANTesters recently such as this one. At the very least these IPv6 tests should be hidden behind a TEST_IPV6 environment variable.

    #   Failed test 'right "Content-Length" value'
    #   at t/mojo/cgi.t line 202.
    #          got: '15'
    #     expected: '17'
    #   Failed test 'right content'
    #   at t/mojo/cgi.t line 204.
    #          got: '127.0.0.1:https'
    #     expected: '10.10.10.10:https'
    # Looks like you failed 2 tests of 6.

#   Failed test 'Trusted proxies'
#   at t/mojo/cgi.t line 205.
# Looks like you failed 1 test of 9.
t/mojo/cgi.t ............................... 
Dubious, test returned 1 (wstat 256, 0x100)
Failed 1/9 subtests 
t/mojo/reactor_poll.t ...................... ok
t/mojo/request.t ........................... ok
t/mojo/request_cgi.t ....................... ok
t/mojo/response.t .......................... ok
t/mojo/roles.t ............................. skipped: Role::Tiny 2.000001+ required for this test!
t/mojo/signatures.t ........................ skipped: Perl 5.20+ required for this test!
t/mojo/subprocess.t ........................ skipped: set TEST_SUBPROCESS to enable this test (developer only!)
t/mojo/subprocess_ev.t ..................... skipped: set TEST_SUBPROCESS to enable this test (developer only!)
t/mojo/template.t .......................... ok
t/mojo/tls.t ............................... skipped: set TEST_TLS to enable this test (developer only!)
t/mojo/transactor.t ........................ ok
t/mojo/url.t ............................... ok
t/mojo/user_agent.t ........................ ok
t/mojo/user_agent_online.t ................. skipped: set TEST_ONLINE to enable this test (developer only!)
t/mojo/user_agent_socks.t .................. skipped: set TEST_SOCKS to enable this test (developer only!)
t/mojo/user_agent_tls.t .................... skipped: set TEST_TLS to enable this test (developer only!)
t/mojo/user_agent_unix.t ................... skipped: set TEST_UNIX to enable this test (developer only!)
    
    #   Failed test 'oversize v6 mask'
    #   at t/mojo/util.t line 493.
    
    #   Failed test 'v6 network contains addresss'
    #   at t/mojo/util.t line 516.
    
    #   Failed test 'v6 network contains addresss'
    #   at t/mojo/util.t line 517.
    
    #   Failed test 'v6 network contains addresss'
    #   at t/mojo/util.t line 518.
    
    #   Failed test 'v6 network contains addresss'
    #   at t/mojo/util.t line 519.
    
    #   Failed test 'v6 network contains addresss'
    #   at t/mojo/util.t line 520.
    
    #   Failed test 'v6 network contains addresss'
    #   at t/mojo/util.t line 521.
    
    #   Failed test 'v6 network contains addresss'
    #   at t/mojo/util.t line 522.
    
    #   Failed test 'v6 network contains addresss'
    #   at t/mojo/util.t line 523.
    
    #   Failed test 'v6 network contains addresss'
    #   at t/mojo/util.t line 524.
    
    #   Failed test 'v6 network contains addresss'
    #   at t/mojo/util.t line 525.
    
    #   Failed test 'v6 network contains addresss'
    #   at t/mojo/util.t line 526.
    
    #   Failed test 'v6 network contains addresss'
    #   at t/mojo/util.t line 527.
    
    #   Failed test 'v6 network contains addresss'
    #   at t/mojo/util.t line 528.
    
    #   Failed test 'v6 network contains addresss'
    #   at t/mojo/util.t line 529.
    
    #   Failed test 'v6 network contains addresss'
    #   at t/mojo/util.t line 530.
    
    #   Failed test 'v6 network contains addresss'
    #   at t/mojo/util.t line 531.
    
    #   Failed test 'v6 network contains addresss'
    #   at t/mojo/util.t line 532.
    # Looks like you failed 18 tests of 62.

#   Failed test 'network_contains'
#   at t/mojo/util.t line 552.
# Looks like you failed 1 test of 61.
t/mojo/util.t .............................. 
Dubious, test returned 1 (wstat 256, 0x100)
Failed 1/61 subtests