Force LocalFile::purgeMetadataCache use the master DB
This used to happen automatically via markVolatile() but that was
removed in I808c3a6, which caused cache updates after move/delete
to retain outdated information from slaves.
Bug: T93009
Bug: T88506
Change-Id: Ie4a6c5fbecec9b38ad3ff45fbc22c5d74d66601c
(cherry picked from commit 00e925fe9200ae0808a240a567afc43bf3a456d5)