vfs_virusfilter: Allocate separate memory for config char*

vfs_virusfilter: Allocate separate memory for config char*

Instead of using only the pointer to the configuration char* from the
global configuration, vfs_virusfilter now allocates its own memory and
copies the char* from the global configuration.

BUG: https://bugzilla.samba.org/show_bug.cgi?id=14606
Signed-off-by: Arne Kreddig <arne@kreddig.net>
Reviewed-by: Volker Lendecke <vl@samba.org>
Reviewed-by: Jeremy Allison <jra@samba.org>
Autobuild-User(master): Jeremy Allison <jra@samba.org>
Autobuild-Date(master): Thu Jan  7 19:25:38 UTC 2021 on sn-devel-184