Retry rfcomm socket connections after link key exchange error.

If the devices were paired before, but unpaired on the
remote end, it will return an error (when sending a file)for the auth
request for the socket connection. Link keys will get exchanged
but we need to retry the socket connection. There is no good way to
inform this socket asking it to retry apart from
a delayed retry. The socket is opened at the kernel level
but the link key retrys happen at the Bluez userspace level.

Note: This is a temporary change, once the new mgmt interface comes
up in Bluez, we wouldn't need this.

Change-Id: Ifbd93d7f69b93515dda6c6f4ad2796853f9d5841