flaky TestTcpSimultaneousConnect test

[marten-seemann]

=== RUN   TestTcpSimultaneousConnect
      libp2p_test.go:231: 
          	Error Trace:	libp2p_test.go:231
          	            				asm_386.s:1315
          	Error:      	Received unexpected error:
          	            	failed to dial QmWSsAXRCm4TRAs7qedhUAxzTuCxkwJAger2FygN82KrkU:
          	            	  * [/ip4/10.1.1.237/tcp/50234] dial backoff
          	            	  * [/ip4/127.0.0.1/tcp/50234] dial backoff
          	Test:       	TestTcpSimultaneousConnect
  --- FAIL: TestTcpSimultaneousConnect (2.82s)

[marten-seemann]

This might be the same failure as in #1208.

[marten-seemann]

Also happening on OSX:

=== RUN   TestTcpSimultaneousConnect
      libp2p_test.go:207: 
          	Error Trace:	libp2p_test.go:207
          	            				asm_amd64.s:1371
          	Error:      	Received unexpected error:
          	            	failed to dial QmRqjPgN9EYBZcEK9qHMuKKrQGutmWumy2LkhBauAy2Fgs:
          	            	  * [/ip4/10.79.9.10/tcp/49467] failed to negotiate security protocol: error reading handshake message: read tcp4 10.79.9.10:49468->10.79.9.10:49467: read: connection reset by peer
          	            	  * [/ip4/127.0.0.1/tcp/49467] failed to negotiate security protocol: failed to secure inbound connection: error reading handshake message: read tcp4 127.0.0.1:49468->127.0.0.1:49467: read: connection reset by peer
          	Test:       	TestTcpSimultaneousConnect
  --- FAIL: TestTcpSimultaneousConnect (1.25s)