MXS-1591 Mark GET_LOCK(...) et.al. as WRITE

The follwing statements

    SELECT GET_LOCK('lock1',10);
    SELECT IS_FREE_LOCK('lock1');
    SELECT IS_USED_LOCK('lock1');
    SELECT RELEASE_LOCK('lock1');

are now classified as QUERY_TYPE_READ|QUERY_TYPE_WRITE. That will
make cooperative locking work if these functions are used inside
non-read-only transactions and outside transanctions.

query_classifier/test/input.sql

@@ -19,3 +19,7 @@ select if(@@hostname='box02','prod_mariadb02','n');
 select next value for seq1;
 select nextval(seq1);
 select seq1.nextval;
+SELECT GET_LOCK('lock1',10);
+SELECT IS_FREE_LOCK('lock1');
+SELECT IS_USED_LOCK('lock1');
+SELECT RELEASE_LOCK('lock1');