Install curl when logstash watchdog is used.

The logstash watchdog depends on curl and assumed that curl would just
be available. Not all cloud images are created equal and come with curl.
Be explicit about the need for curl and install it with puppet in the
watchdog manifest.

Change-Id: If90cae9a64b9f48f04b5643b643d2c83650c7d86
Merge "Install curl when logstash watchdog is used."