Add tags_filename parameter to update_tag method
Add tags_filename parameter to update_tag method

Currently, file name for tags file is hardcoded to
<tag_type>/<tag_name>.yml. While this is true for rdoinfo, it may be
different in other distroinfo based repos, as nfvinfo.

This patch is adding a new parameter tags_filename to set the name of
the file used for tags update.

Change-Id: I2f80d9278a114f125b7fe36804bc489f8466db50

rdo-infra/releng,rdo-infra/releng