Changes

statsd: Support f_statsd_snapshot() API when using VTY-triggered stats report

Until now that API was only used in testsuites which relied on
time-trigerred reports. This commit also supports getting a given
snapshots if the IUT is configured to only trigger a report based on VTY
request.

Change-Id: I87d34e2f365d3b71ce328c08999be43d482326ad