typo in xtrabackup script

Change-Id: I49f75fe9501312e0283ff8bcd292c54ec456dbd5
Related-prod: PROD-28535
diff --git a/xtrabackup/files/innobackupex-client-runner.sh b/xtrabackup/files/innobackupex-client-runner.sh
index a5d14c9..19a34ba 100644
--- a/xtrabackup/files/innobackupex-client-runner.sh
+++ b/xtrabackup/files/innobackupex-client-runner.sh
@@ -164,7 +164,7 @@
     echo "Number of Incremental backups stored: " $NUMBER_OF_INCR
     echo "----------------------------"
     #If number of incremental mod number of full backups to keep equals 1, run full backup, otherwise run incremental
-    if [ $(( ($NUMBER_OF_INCR + $NUMBER_OF_FULL) % ($INCRBEFOREFULL + 1) )) -eq 0 || FORCEFULL=true ] ; then
+    if [ $(( ($NUMBER_OF_INCR + $NUMBER_OF_FULL) % ($INCRBEFOREFULL + 1) )) -eq 0 ] || [ FORCEFULL=true ] ; then
       echo "Running new full backup."
       innobackupex --defaults-file=$MYCNF $USEROPTIONS $compress $compression_threads $FULLBACKUPDIR 2>&1 | tee $TMPFILE
     else