libtracker-sparql: Fix deadlock when tracker is not available
libtracker-sparql: Fix deadlock when tracker is not available

If a connection attempt failed, subsequent connection attempts
deadlocked.

hoheinzollern/tracker,hoheinzollern/tracker,outofbits/tracker,hoheinzollern/tracker,outofbits/tracker,outofbits/tracker,outofbits/tracker,hoheinzollern/tracker,hoheinzollern/tracker,hoheinzollern/tracker,outofbits/tracker,outofbits/tracker,outofbits/tracker,hoheinzollern/tracker