cephfs: fix variable declared in conditional statement

Signed-off-by: Thomas Lamprecht <t.lamprecht@proxmox.com>

PVE/Storage/CephFSPlugin.pm

@@ -170,8 +170,7 @@ sub check_config {
 sub on_add_hook {
     my ($class, $storeid, $scfg, %param) = @_;
 
-    my $secret = $param{keyring} if defined $param{keyring} // undef;
-    PVE::CephConfig::ceph_create_keyfile($scfg->{type}, $storeid, $secret);
+    PVE::CephConfig::ceph_create_keyfile($scfg->{type}, $storeid, $param{keyring});
 
     return;
 }