[stable15] always allow moving mountpoints inside the same mountpoint

[backportbot-nextcloud]

backport of #14691

[faily-bot]

🤖 beep boop beep 🤖

Here are the logs for the failed build:

Status of 17162: failure

TESTS=acceptance, TESTS-ACCEPTANCE=app-comments

• tests/acceptance/features/app-comments.feature:56

Show full log

  Scenario: read a comment written by the sharee             # /drone/src/github.com/nextcloud/server/tests/acceptance/features/app-comments.feature:56
    Given I act as John                                      # ActorContext::iActAs()
    And I am logged in as the admin                          # LoginPageContext::iAmLoggedInAsTheAdmin()
    And I act as Jane                                        # ActorContext::iActAs()
    And I am logged in                                       # LoginPageContext::iAmLoggedIn()
    And I act as John                                        # ActorContext::iActAs()
    And I rename "welcome.txt" to "shared.txt"               # FileListContext::iRenameTo()
    And I share "shared.txt" with "user0"                    # FilesAppSharingContext::iShareWith()
      │ Share with input in the details view in Files app value could not be set
      │ Exception message: Element is not currently visible and so may not be interacted with
      │ Build info: version: '2.53.1', revision: 'a36b8b1', time: '2016-06-30 17:37:03'
      │ System info: host: 'a9323126387d', ip: '172.17.0.5', os.name: 'Linux', os.arch: 'amd64', os.version: '4.15.0-43-generic', java.version: '1.8.0_91'
      │ Driver info: driver.version: unknown
      │ Trying again
      │ 
    And I see that the file is shared with "user0"           # FilesAppSharingContext::iSeeThatTheFileIsSharedWith()
    And I act as Jane                                        # ActorContext::iActAs()
    And I open the Files app                                 # FilesAppContext::iOpenTheFilesApp()
    And I open the details view for "shared.txt"             # FileListContext::iOpenTheDetailsViewFor()
    And I open the "Comments" tab in the details view        # FilesAppContext::iOpenTheTabInTheDetailsView()
    And I create a new comment with "Hello world" as message # CommentsAppContext::iCreateANewCommentWithAsMessage()
    And I see a comment with "Hello world" as message        # CommentsAppContext::iSeeACommentWithAsMessage()
    When I act as John                                       # ActorContext::iActAs()
    And I open the Files app                                 # FilesAppContext::iOpenTheFilesApp()
    And I open the details view for "shared.txt"             # FileListContext::iOpenTheDetailsViewFor()
      Row for file shared.txt in file list could not be found after 100 seconds
      File actions menu button for file shared.txt in file list could not be found after 100 seconds (NoSuchElementException)
    And I open the "Comments" tab in the details view        # FilesAppContext::iOpenTheTabInTheDetailsView()
    Then I see a comment with "Hello world" as message       # CommentsAppContext::iSeeACommentWithAsMessage()
sh: 1: kill: No such process

[MorrisJobke]

Code makes sense 👍