mariadb: change socket location in my.cnf

Change socket location to /var/lib/mysql/mysql.sock. Otherwise, we
could spot errors in systemd systems like below.

mysqladmin: connect to server at 'localhost' failed
error: 'Can't connect to local MySQL server through socket '/tmp/mysql.sock' (2)'
Check that mysqld is running and that the socket: '/tmp/mysql.sock' exists!

This is because mysqld.service is using PrivateTmp=true.

Signed-off-by: Chen Qi <Qi.Chen@windriver.com>
Signed-off-by: Martin Jansa <Martin.Jansa@gmail.com>

meta-oe/recipes-support/mysql/mariadb/my.cnf

@@ -1,7 +1,7 @@
 [client]
 #password					= password
 port						= 3306
-socket						= /tmp/mysql.sock
+socket						= /var/lib/mysql/mysql.sock
 
 [mysqld_safe]
 err-log						= /var/log/mysql.err
@@ -9,7 +9,7 @@ err-log						= /var/log/mysql.err
 [mysqld]
 user 						= mysql
 port 						= 3306
-socket 						= /tmp/mysql.sock
+socket 						= /var/lib/mysql/mysql.sock
 pid-file 					= /var/lib/mysql/mysqld.pid
 log-error 					= /var/log/mysqld.err
 basedir 					= /usr