Wrong path used for mysqld

rhbz: #1403416

diff -up mariadb-10.1.28/scripts/galera_recovery.sh.p43 mariadb-10.1.28/scripts/galera_recovery.sh
--- mariadb-10.1.28/scripts/galera_recovery.sh.p43	2017-11-10 00:28:01.843757434 +0100
+++ mariadb-10.1.28/scripts/galera_recovery.sh	2017-11-10 00:28:51.827998710 +0100
@@ -68,7 +68,7 @@ parse_arguments() {
 
 wsrep_recover_position() {
   # Redirect server's error log to the log file.
-  eval /usr/sbin/mysqld $cmdline_args --user=$user --wsrep_recover \
+  eval @libexecdir@/mysqld $cmdline_args --user=$user --wsrep_recover \
     --disable-log-error 2> "$log_file"
   ret=$?
   if [ $ret -ne 0 ]; then