Also propagate etag changes when the watcher finds a changed file
Merge pull request #11575 from owncloud/cache-watcher-propagate

Propagate etag changes when the watcher finds a changed file
also try to get file info from part file
don't scan part files
only set the values we need and make sure that we write the file info for both
the real file and the part file, because some information from the part file
might be needed later
Merge pull request #11736 from owncloud/enc_get_fileinfo_from_real_file

if we read a .part file we try to get the file info from the real file
Convert StorageNotAvailableException to SabreDAV exception

Convert \OCP\Files\StorageNotAvailableException to
\Sabre\DAV\Exception\ServiceUnavailable for every file/directory
operation happening inside of SabreDAV.

This is necessary to avoid having the exception bubble up to remote.php
which would return an exception page instead of an appropriate response.