provision/swarm: prevents data race with mutex in shell tests
provision/swarm: prevents data race with mutex in shell tests

WARNING: DATA RACE
Read by goroutine 338:
  github.com/tsuru/tsuru/provision/swarm.(*S).TestShellToAnAppByAppName.func2()
      /tmp/gopath/tsuru/src/github.com/tsuru/tsuru/provision/swarm/provisioner_test.go:1140 +0x9c
  github.com/tsuru/tsuru/vendor/github.com/fsouza/go-dockerclient/testing.(*DockerServer).ServeHTTP()
      /tmp/gopath/tsuru/src/github.com/tsuru/tsuru/vendor/github.com/fsouza/go-dockerclient/testing/server.go:338 +0x312
  net/http.serverHandler.ServeHTTP()
      /usr/local/go/src/net/http/server.go:2081 +0x206
  net/http.(*conn).serve()
      /usr/local/go/src/net/http/server.go:1472 +0x1565

Previous write by goroutine 133:
  github.com/tsuru/tsuru/provision/swarm.(*S).TestShellToAnAppByAppName.func2()
      /tmp/gopath/tsuru/src/github.com/tsuru/tsuru/provision/swarm/provisioner_test.go:1140 +0x180
  github.com/tsuru/tsuru/vendor/github.com/fsouza/go-dockerclient/testing.(*DockerServer).ServeHTTP()
      /tmp/gopath/tsuru/src/github.com/tsuru/tsuru/vendor/github.com/fsouza/go-dockerclient/testing/server.go:338 +0x312
  net/http.serverHandler.ServeHTTP()
      /usr/local/go/src/net/http/server.go:2081 +0x206
  net/http.(*conn).serve()
      /usr/local/go/src/net/http/server.go:1472 +0x1565

Goroutine 338 (running) created at:
  net/http.(*Server).Serve()
      /usr/local/go/src/net/http/server.go:2137 +0x4d1
  net/http.Serve()
      /usr/local/go/src/net/http/server.go:1976 +0xce

Goroutine 133 (finished) created at:
  net/http.(*Server).Serve()
      /usr/local/go/src/net/http/server.go:2137 +0x4d1
  net/http.Serve()
      /usr/local/go/src/net/http/server.go:1976 +0xce
==================
==================
WARNING: DATA RACE
Read by goroutine 43:
  github.com/tsuru/tsuru/provision/swarm.(*S).TestShellToAnAppByTaskID.func2()
      /tmp/gopath/tsuru/src/github.com/tsuru/tsuru/provision/swarm/provisioner_test.go:1192 +0x9c
  github.com/tsuru/tsuru/vendor/github.com/fsouza/go-dockerclient/testing.(*DockerServer).ServeHTTP()
      /tmp/gopath/tsuru/src/github.com/tsuru/tsuru/vendor/github.com/fsouza/go-dockerclient/testing/server.go:338 +0x312
  net/http.serverHandler.ServeHTTP()
      /usr/local/go/src/net/http/server.go:2081 +0x206
  net/http.(*conn).serve()
      /usr/local/go/src/net/http/server.go:1472 +0x1565

Previous write by goroutine 73:
  github.com/tsuru/tsuru/provision/swarm.(*S).TestShellToAnAppByTaskID.func2()
      /tmp/gopath/tsuru/src/github.com/tsuru/tsuru/provision/swarm/provisioner_test.go:1192 +0x180
  github.com/tsuru/tsuru/vendor/github.com/fsouza/go-dockerclient/testing.(*DockerServer).ServeHTTP()
      /tmp/gopath/tsuru/src/github.com/tsuru/tsuru/vendor/github.com/fsouza/go-dockerclient/testing/server.go:338 +0x312
  net/http.serverHandler.ServeHTTP()
      /usr/local/go/src/net/http/server.go:2081 +0x206
  net/http.(*conn).serve()
      /usr/local/go/src/net/http/server.go:1472 +0x1565

Goroutine 43 (running) created at:
  net/http.(*Server).Serve()
      /usr/local/go/src/net/http/server.go:2137 +0x4d1
  net/http.Serve()
      /usr/local/go/src/net/http/server.go:1976 +0xce

Goroutine 73 (finished) created at:
  net/http.(*Server).Serve()
      /usr/local/go/src/net/http/server.go:2137 +0x4d1
  net/http.Serve()
      /usr/local/go/src/net/http/server.go:1976 +0xce
==================

tsuru/tsuru,cezarsa/tsuru,tsuru/tsuru,tsuru/tsuru,ArxdSilva/tsuru,gwmoura/tsuru,guilhermebr/tsuru,cezarsa/tsuru,ArxdSilva/tsuru,gwmoura/tsuru,guilhermebr/tsuru,cezarsa/tsuru,ArxdSilva/tsuru,ggarnier/tsuru,ggarnier/tsuru,gwmoura/tsuru,guilhermebr/tsuru,ArxdSilva/tsuru,tsuru/tsuru,guilhermebr/tsuru,ggarnier/tsuru,ggarnier/tsuru,cezarsa/tsuru