MDEV-10538: MariaDB fails to start without galera_recovery in systemd mode

Update ExecStartPre scripts to not fail if 'galera_recovery'
script is not available.

support-files/mariadb.service.in

@@ -63,9 +63,11 @@ PermissionsStartOnly=true
 # galera_recovery simply returns an empty string. In any case, however,
 # the script is not expected to return with a non-zero status.
 # It is always safe to unset _WSREP_START_POSITION environment variable.
+# Do not panic if galera_recovery script is not available. (MDEV-10538)
 ExecStartPre=/bin/sh -c "systemctl unset-environment _WSREP_START_POSITION"
-ExecStartPre=/bin/sh -c "VAR=`/usr/bin/galera_recovery`; [ $? -eq 0 ] && \
- systemctl set-environment _WSREP_START_POSITION=$VAR || exit 1"
+ExecStartPre=/bin/sh -c "[ ! -e /usr/bin/galera_recovery ] && VAR= || \
+ VAR=`/usr/bin/galera_recovery`; [ $? -eq 0 ] \
+ && systemctl set-environment _WSREP_START_POSITION=$VAR || exit 1"
 
 # Needed to create system tables etc.
 # ExecStartPre=/usr/bin/mysql_install_db -u mysql

support-files/mariadb@.service.in

@@ -70,16 +70,19 @@ PermissionsStartOnly=true
 # galera_recovery simply returns an empty string. In any case, however,
 # the script is not expected to return with a non-zero status.
 # It is always safe to unset _WSREP_START_POSITION%I environment variable.
+# Do not panic if galera_recovery script is not available. (MDEV-10538)
 ExecStartPre=/bin/sh -c "systemctl unset-environment _WSREP_START_POSITION%I"
-ExecStartPre=/bin/sh -c "VAR=`/usr/bin/galera_recovery             \
-  --defaults-file=@INSTALL_SYSCONF2DIR@/my%I.cnf`; [ $? -eq 0 ] && \
-  systemctl set-environment _WSREP_START_POSITION%I=$VAR || exit 1"
+
+ExecStartPre=/bin/sh -c "[ ! -e /usr/bin/galera_recovery ] && VAR= || \
+ VAR=`/usr/bin/galera_recovery --defaults-file=@INSTALL_SYSCONF2DIR@/my%I.cnf`; [ $? -eq 0 ] \
+ && systemctl set-environment _WSREP_START_POSITION%I=$VAR || exit 1"
+
 # Alternate: (remove ConditionPathExists above)
 # use [mysqld.INSTANCENAME] as sections in my.cnf
 #
-#ExecStartPre=/bin/sh -c "VAR=`/usr/bin/galera_recovery \
-# --defaults-group-suffix=%I`; [ $? -eq 0 ] &&          \
-# systemctl set-environment _WSREP_START_POSITION%I=$VAR || exit 1"
+#ExecStartPre=/bin/sh -c "[ ! -e /usr/bin/galera_recovery ] && VAR= || \
+# VAR=`/usr/bin/galera_recovery --defaults-group-suffix=%I`; [ $? -eq 0 ] \
+# && systemctl set-environment _WSREP_START_POSITION%I=$VAR || exit 1"
 
 # Needed to create system tables etc.
 # ExecStartPre=/usr/bin/mysql_install_db -u mysql