s3/rpc_server: track the number of policy handles with a talloc destructor

s3/rpc_server: track the number of policy handles with a talloc destructor

BUG: https://bugzilla.samba.org/show_bug.cgi?id=14783
RN: smbd "deadtime" parameter doesn't work anymore

Signed-off-by: Ralph Boehme <slow@samba.org>
Reviewed-by: Samuel Cabrero <scabrero@samba.org>
Reviewed-by: Jeremy Allison <jra@samba.org>
Autobuild-User(master): Jeremy Allison <jra@samba.org>
Autobuild-Date(master): Tue Aug 10 18:41:43 UTC 2021 on sn-devel-184

(cherry picked from commit 45a33b25c4e6b1db5d2dfa6297ccb390220a7c80)

Autobuild-User(v4-15-test): Jule Anger <janger@samba.org>
Autobuild-Date(v4-15-test): Thu Aug 26 14:30:56 UTC 2021 on sn-devel-184