Remove const cast from leaf functions.

Remove const cast from leaf functions.

app_control_register_rule and app_control_unregister_rule lock/unlock
the queue, which is a mutating operation according to the
ao2_lock/_unlock prototype. Depending on the specific (implicit) casts
in SCOPED_LOCK and RAII_VAR, the compiler may warn or not. As the only
callers of those functions do not have the const, get consistent results
by just dropping it.

Change-Id: Ib9e6296155a39bc5d627142a3828180c3cfe8fbb