plugin: hooks: add explicit returns

to avoid returning something unexpected. Finish what
afeda18256 already started for all the other
plugins. At least for ZFS's on_add_hook this is necessary (adding a ZFS storage
currently fails as reported here [0]), but it cannot hurt
in the other places either as the only hooks we expect to return something
currently are PBS's on_add_hook and on_update_hook.

[0]: https://forum.proxmox.com/threads/gui-add-zfs-storage-verification-failed-400-config-type-check-object-failed.79734/

Signed-off-by: Fabian Ebner <f.ebner@proxmox.com>

PVE/Storage/CIFSPlugin.pm

@@ -168,6 +168,8 @@ sub on_add_hook {
     } else {
 	cifs_delete_credentials($storeid);
     }
+
+    return;
 }
 
 sub on_update_hook {
@@ -183,12 +185,16 @@ sub on_update_hook {
     } else {
 	cifs_delete_credentials($storeid);
     }
+
+    return;
 }
 
 sub on_delete_hook {
     my ($class, $storeid, $scfg) = @_;
 
     cifs_delete_credentials($storeid);
+
+    return;
 }
 
 sub status {

PVE/Storage/CephFSPlugin.pm

@@ -170,6 +170,8 @@ sub on_add_hook {
     return if defined($scfg->{monhost}); # nothing to do if not pve managed ceph
 
     PVE::CephConfig::ceph_create_keyfile($scfg->{type}, $storeid);
+
+    return;
 }
 
 sub on_delete_hook {
@@ -178,6 +180,8 @@ sub on_delete_hook {
     return if defined($scfg->{monhost}); # nothing to do if not pve managed ceph
 
     PVE::CephConfig::ceph_remove_keyfile($scfg->{type}, $storeid);
+
+    return;
 }
 
 sub status {

PVE/Storage/LVMPlugin.pm

@@ -269,6 +269,8 @@ sub on_add_hook {
 
 	lvm_create_volume_group($path, $scfg->{vgname}, $scfg->{shared});
     }
+
+    return;
 }
 
 sub parse_volname {

PVE/Storage/PBSPlugin.pm

@@ -452,6 +452,8 @@ sub on_delete_hook {
 
     pbs_delete_password($scfg, $storeid);
     pbs_delete_encryption_key($scfg, $storeid);
+
+    return;
 }
 
 sub parse_volname {

PVE/Storage/RBDPlugin.pm

@@ -317,6 +317,8 @@ sub on_add_hook {
     return if defined($scfg->{monhost}); # nothing to do if not pve managed ceph
 
     PVE::CephConfig::ceph_create_keyfile($scfg->{type}, $storeid);
+
+    return;
 }
 
 sub on_delete_hook {
@@ -325,6 +327,8 @@ sub on_delete_hook {
     return if defined($scfg->{monhost}); # nothing to do if not pve managed ceph
 
     PVE::CephConfig::ceph_remove_keyfile($scfg->{type}, $storeid);
+
+    return;
 }
 
 sub parse_volname {

PVE/Storage/ZFSPoolPlugin.pm

@@ -133,6 +133,8 @@ sub on_add_hook {
     } else {
 	$scfg->{mountpoint} = $mountpoint;
     }
+
+    return;
 }
 
 sub path {