libtracker-data: Backup in separate thread in single step
libtracker-data: Backup in separate thread in single step

Using SQLite backup in multiple steps may restart the process due to
concurrent update operations.

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