kes Implement bsock code to permit locking. Use the new code in Verify

kes  Implement bsock code to permit locking. Use the new code in Verify
     in the FD to prevent the heartbeat thread from disrupting the Verify
     data sent to the Dir.
kes  Modify SD locking to eliminate locking the reservations system from
     outside the system. Use the volume lock when getting media data
     and reserving a new volume at end of media.
kes  Add Eric's volume_unused() fix to stored.c so that Volumes found
     when SD starts are not locked into place.

git-svn-id: https://bacula.svn.sourceforge.net/svnroot/bacula/trunk@6694 91ce42f0-d328-0410-95d8-f526ca767f89