Fix mysql bindings

There was a copy paste error in the Makefile of the mysql dlz modules,
instead of setting the MYSQL_LIBS, LDAP_LIBS where set. This caused
the mysql bindings not to be generated.

(cherry picked from commit 38c74005)
68 jobs for !6639 with 3479-mysql-is-not-ldap-v9_18 in 34 minutes and 55 seconds (queued for 5 seconds)
latest merge request