SD to SD replication makes SD crash

Problem is that we wait up to 30 minutes for the SD-SD replication
job to start but it could be that the total migration/copy run takes
longer then 30 minutes to finish all jobs. The current code doesn't take
this into consideration and doesn't check if there is actually a remote
SD that connected for doing the replication.

So fix is to not continue when sd replication socket is not connected.
And also remove the timeout on starting a SD-SD replication session.
The normal FD-SD connection is protected with a timeout so we don't hang
when a FD never connects. As we support canceling a storage Job from the
director and the director should cleanly cancel the storage job any way
when it fails the copy or migration job it should be no problem.

In a normal backup/restore there are 3 daemons involved e.g. director,
storage daemon and file daemon but with migration the director controls
everything and controls the at maximum two storage daemons.

Fixes #276: SD to SD replication makes SD crash