[stable7] Fix size propagation over shared storage boundary

[PVince81]

Backport of #14720 to stable7

@icewind1991 @nickvergessen @MorrisJobke

(there were merge conflicts)

[PVince81]

Had a quick manual test, it works.

I'll fix the unit test.

[PVince81]

Having trouble with the unit tests.
It looks like on stable7 there is a stat cache issue. When re-reading the filesize after simulated upload, it still returns the old size. I need to add an explicit clearstatcache($fullPath) here https://github.com/owncloud/core/blob/stable7/lib/private/files/storage/local.php#L113 to make it work.

I'll try and find out why it works on master... maybe something else needs backporting.

[PVince81]

Okay, it seems that backporting #10881 would fix it.
Even though that linked PR is about clearstatcache for mtime, it has the side effect of also making it work for the size...

[scrutinizer-notifier]

A new inspection was created.

[PVince81]

I have now backported the commits from #10881 (comment) here, let me know if this is ok.

[scrutinizer-notifier]

The inspection completed: 3 new issues, 4 updated code elements

[karlitschek]

backport is fine. 👍

[PVince81]

A Jenkins PR even for stable7 ?! Pffff...
Maybe I should stop pushing furiously.

Here it is: #14934

[PVince81]

Please review

[PVince81]

Test steps here: #14596 (comment)

[MorrisJobke]

Tested and works 👍