[stable15] dav: Fix handling of chunked WebDAV upload

[backportbot-nextcloud]

backport of #13871

[faily-bot]

🤖 beep boop beep 🤖

Here are the logs for the failed build:

Status of 16724: failure

• DB=mysqlmb4, ENABLE_REDIS=false, PHP=7.3

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There was 1 failure:
1) TrashbinTest::testExpireOldFiles
Failed asserting that null is identical to 'file2.txt'.
/drone/src/github.com/nextcloud/server/apps/files_trashbin/tests/TrashbinTest.php:186
--
There was 1 risky test:
1) OCA\TwoFactorBackupCodes\Tests\Db\BackupCodeMapperTest::testInsertArgonEncryptedCodes
This test did not perform any assertions

• TESTS=acceptance, TESTS-ACCEPTANCE=app-files-sharing-link
  • tests/acceptance/features/app-files-sharing-link.feature:81

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 Scenario: owner sees folder created in the public page of an editable shared folder # /drone/src/github.com/nextcloud/server/tests/acceptance/features/app-files-sharing-link.feature:81
Given I act as John # ActorContext::iActAs()
And I am logged in # LoginPageContext::iAmLoggedIn()
And I create a new folder named "Editable shared folder" # FileListContext::iCreateANewFolderNamed()
And I close the details view # FilesAppContext::iCloseTheDetailsView()
And I see that the details view is closed # FilesAppContext::iSeeThatTheDetailsViewIsClosed()
And I share the link for "Editable shared folder" # FilesAppSharingContext::iShareTheLinkFor()
And I set the shared link as editable # FilesAppSharingContext::iSetTheSharedLinkAsEditable()
And I write down the shared link # FilesAppSharingContext::iWriteDownTheSharedLink()
Element is no longer attached to the DOM
For documentation on this error, please visit: http://seleniumhq.org/exceptions/stale_element_reference.html
Build info: version: '2.53.1', revision: 'a36b8b1', time: '2016-06-30 17:37:03'
System info: host: 'ba1f1ef28e3d', ip: '172.17.0.11', os.name: 'Linux', os.arch: 'amd64', os.version: '4.15.0-43-generic', java.version: '1.8.0_91'
Driver info: driver.version: unknown (WebDriver\Exception\StaleElementReference)
And I act as Jane # ActorContext::iActAs()
And I visit the shared link I wrote down # PublicShareContext::iVisitTheSharedLinkIWroteDown()
And I see that the current page is the shared link I wrote down # PublicShareContext::iSeeThatTheCurrentPageIsTheSharedLinkIWroteDown()
And I create a new folder named "Subfolder" # FileListContext::iCreateANewFolderNamed()
And I see that the file list contains a file named "Subfolder" # FileListContext::iSeeThatTheFileListContainsAFileNamed()
When I act as John # ActorContext::iActAs()
And I enter in the folder named "Editable shared folder" # FileListContext::iEnterInTheFolderNamed()
Then I see that the file list contains a file named "Subfolder" # FileListContext::iSeeThatTheFileListContainsAFileNamed()

[MorrisJobke]

Code makes sense 👍

[ariselseng]

Looks good to me.