Libprocess links will not generate an ExitedEvent if the socket creation fails

Noticed this while inspecting nearby code for potential races.

Normally, when a libprocess actor (the "linkee") links to a remote process, it does the following:
1) Create a socket.
2) Connect to the remote process (asynchronous).
3) Check the connection succeeded.

If (2) or (3) fail, the linkee will receive a ExitedEvent, which indicates that the link broke. In case (1) fails, there is no ExitedEvent:
https://github.com/apache/mesos/blob/7c833abbec9c9e4eb51d67f7a8e7a8d0870825f8/3rdparty/libprocess/src/process.cpp#L1558-L1562