MDEV-31737 : Node never returns from Donor/Desynced to Synced when wsrep_mode = BF_ABORT_MARIABACKUP

Problem was incorrect condition when node should have
resumed and resync at backup_end. Simplified condition
to fix the problem and added missing test case for
this wsrep_mode = BF_ABORT_MARIABACKUP.
Signed-off-by: Julius Goryavsky <julius.goryavsky@mariadb.com>