Fix and refactor passive exchange/queue tests

Split tests that don't require cross-channel communication.
Skip flow control test when not implemented
Refactor test helper to have single return
Support go1.0 lack of testing.T.Skip()
Fixes formatting type mismatch in tests
Fixes returning a lock(amqp.consumers) by value
Merge pull request #103 from sudorandom/govet-fixes

Fixes current go vet warnings
Merge branch 'master' of github.com:streadway/amqp