Slave when bound to localhost cannot connect to master(system api connect return error:inprogress)

[europelee]

Hi, guys:
As issue title, there exists similar issue, but still some difference in the issue.
the key point is that system api connect function return error:inprogress in anetTcpGenericConnect of anetTcpNonBlockBestEffortBindConnect calling when slave binding lo interface, so the call is never retried without source address binding attempt, slave would never connect to master successfully, and network status is always on SYN_SENT. @antirez @pietern @mattsta