Adds Trove mock to tests in database_backups

Test cases in database_backups/tests.py now have a mock for the
method api.trove.instance_get(). The absence of this mock was
causing real HTTP requests to Trove.

Change-Id: Icf760d7eaba2d136626dbbbbf6e49260a18fb874
Closes-Bug: #1255936
Allow translators to control word order of BatchAction message

Currently BatchAction message is generated by concatenating
'action' and 'data_type'. In most cases 'action' is a verb
and 'data_type' is an object. However in some action such as
TerminateInstance 'action' is a combination of verb and
object (e.g., "Scheduled termination of").  It is hard that
translators find translated strings which covers both cases.

This commit allows classes inheriting BatchAction to specify
a full action name containing '%(data_type)s' substitution
in action_present/ action_past so that translators can
control the order of phrases completely.

* _conjugate() in actions.py is renamed to _get_action_name()
  because this method no longer always conjugate words.
* Changes action_past strings which are not a form of verb + obj
  to strings with "%(data_type)s"

Closes-Bug: #1253678
Change-Id: I3cf1dc74e22745eb3a9bd2edc3ec68ed389495b5
Merge "Allow translators to control word order of BatchAction message"
Merge "Adds Trove mock to tests in database_backups"