MDEV-17571 Make systemd timeout behavior more compatible with long Galera SSTs

Set an explicit start and stop timeout of 900 seconds for the
MariaDB Server systemd service

support-files/mariadb.service.in

@@ -120,6 +120,13 @@ UMask=007
 # LOAD DATA INFILE you can enable PrivateTmp=true for a little more security.
 PrivateTmp=false
 
+# Set an explicit Start and Stop timeout of 900 seconds (15 minutes!)
+# this is the same value as used in SysV init scripts in the past
+# Galera might need a longer timeout, check the KB if you want to change this:
+# https://mariadb.com/kb/en/library/systemd/#configuring-the-systemd-service-timeout
+TimeoutStartSec=900
+TimeoutStopSec=900
+
 ##
 ## Options previously available to be set via [mysqld_safe]
 ## that now needs to be set by systemd config files as mysqld_safe

support-files/mariadb@.service.in

@@ -141,6 +141,13 @@ UMask=007
 # LOAD DATA INFILE you can enable PrivateTmp=true for a little more security.
 PrivateTmp=false
 
+# Set an explicit Start and Stop timeout of 900 seconds (15 minutes!)
+# this is the same value as used in SysV init scripts in the past
+# if you need a longer timeout, check the KB:
+# https://mariadb.com/kb/en/library/systemd/#configuring-the-systemd-service-timeout
+TimeoutStartSec=900
+TimeoutStopSec=900
+
 ##
 ## Options previously available to be set via [mysqld_safe]
 ## that now needs to be set by systemd config files as mysqld_safe