xtrabackup was updated to 2.0.7 [bnc#818819]

Changes:
* Time interval between checks done by log copying thread is now
configurable by innobackupex --log-copy-interval.
Bugs fixed:
* Tables that were dropped between taking a full backup and an
incremental one were present in the full backup directory, and
were not removed when incremental backups has been merged
* Percona XtraBackup would leave stale xtrabackup_tmp* files in
the datadir after applying incremental backups.
* Fixed couple of warnings found in innobackupex when all warnings
have been made FATAL.
* If there are thousands of tables and slow IO then XtraBackup
can spend a lot of time opening all the tablespaces. Optimization
has been implemented and XtraBackup now avoids loading
non-relevant tablespaces when partial backup is being taken
which speeds up the backup process.
* Percona XtraBackup didn’t initialize per-thread data in the
log copying thread which could cause XtraBackup to crash.
* innobackupex would still run with FLUSH TABLES WITH READ LOCK
even if xtrabackup would fail when copying logs. Fixed by
terminating xtrabackup process immediately on log copying failure
* innobackupex would fail if the SQL_MODE was set to ANSI_QUOTES.
* Missing space_id from *.ibd.meta would lead to assertion. Fixed
by replacing the assertion with the error message.
* Fixed the typo in the innobackupex error output.
* innobackupex wasn’t handling the innodb_data_file_path option
which could cause backup to fail.
* Redundant code has been removed from xtrabackup.cc.