spoolss: purge the printer name cache on name change

spoolss: purge the printer name cache on name change

Currently the name cache is only cleared on printer deletion. This means
that if a printer undergoes a name change, the old name remains in the
cache and can be subsequently used incorrecly if another printer takes
the same name as the old.

Bug: https://bugzilla.samba.org/show_bug.cgi?id=11210

Reported-by: Franz Pförtsch <franz.pfoertsch@brose.com>
Signed-off-by: David Disseldorp <ddiss@samba.org>
Reviewed-by: Jeremy Allison <jra@samba.org>
Autobuild-User(master): Jeremy Allison <jra@samba.org>
Autobuild-Date(master): Tue Apr 14 05:37:50 CEST 2015 on sn-devel-104

(cherry picked from commit a97507a9a7ba01beead6a621e1210618e93a9f9c)

Autobuild-User(v4-1-test): Karolin Seeger <kseeger@samba.org>
Autobuild-Date(v4-1-test): Tue Apr 21 02:16:00 CEST 2015 on sn-devel-104