Notify the cache the git_tags was modified

The tag cache is updated in-place, which prevents the H2 based
storage from writing out the updated tag information. This means
servers almost never have the right data stored on disk and must
recompute it at startup.

Anytime the value is modified in place, put it back into the
cache so it can be saved for use on the next startup.

Change-Id: Iaa6aa276a40c332e50471c245fe8aad79d9e3f80
5 files changed