[ModifiedFileIndexer] Avoid shadowing XAttr changes by content changes

Summary:
The ModifiedFileIndexer updates the timestamps, which has the effect
the XAttr indexer will not pick up any XAttr changes later when both
happen at approximately the same time.

In case the file metadata has changed, also update everything associated
to the ctime (XAttrs, filename). This also has the nice side effect
of getting rid of a separate BasicIndexingJob run later.

Depends on D21694.

Test Plan:

1. touch testfile; sleep 10
2. setfattr -n baloo.file.rating -v 4 ; touch testfile

After the change, balooshow testfile shows the rating.

Reviewers: Baloo, ngraham, astippich, poboiko

Reviewed By: Baloo, ngraham

Subscribers: kde-frameworks-devel

Tags: Frameworks, Baloo

Differential Revision: https://phabricator.kde.org/D21708