Avoid reset of repeat_actions attribute on alarm update

Fixes bug 1253057

Previously, when an unrelated alarm attribute was updated via the CLI,
the repeat_actions attribute was also set to False as an unwanted side-effect.

Now, we only set this attribute in the update call if explicitly specified
as a CLI arg. Otherwise the value provided in the PUT request body reflects
the pre-existing value for this attribute.

Change-Id: I94468ff649dd4367848c74e94a3feb08494bb223
Merge "Avoid reset of repeat_actions attribute on alarm update"