simplify rename permission

before this patch we allow a rename in the following cases:

- the user has rename permission on both source and target path
- the user has delete permission on source path and create/upload on
  target path

we now check only the rename/rename_files/rename_dirs permissions.
This is what SFTPGo users expect.

This is a backward incompatible change and it will not backported to
the 2.2.x branch

Signed-off-by: Nicola Murino <nicola.murino@gmail.com>

common/protocol_test.go

@@ -1760,7 +1760,8 @@ func TestQuotaRenameToVirtualFolder(t *testing.T) {
 		QuotaSize:  0,
 	})
 	u.Permissions[vdirPath1] = []string{dataprovider.PermListItems, dataprovider.PermDownload, dataprovider.PermUpload,
-		dataprovider.PermOverwrite, dataprovider.PermDelete, dataprovider.PermCreateSymlinks, dataprovider.PermCreateDirs}
+		dataprovider.PermOverwrite, dataprovider.PermDelete, dataprovider.PermCreateSymlinks, dataprovider.PermCreateDirs,
+		dataprovider.PermRename}
 	user, _, err := httpdtest.AddUser(u, http.StatusCreated)
 	assert.NoError(t, err)
 	conn, client, err := getSftpClient(user)