Moves the query_retry method into the baseclass and makes the query
retry and timeout options part of the watcher_datasources config group.
This makes the query_retry behavior uniform across all datasources.
A new baseclass method named query_retry_reset is added so datasources
can define operations to perform when recovering from a query error.
Test cases are added to verify the behavior of query_retry.
The query_max_retries and query_timeout config parameters are
deprecated in the gnocchi_client group and will be removed in a future
release.
Change-Id: I33e9dc2d1f5ba8f83fcf1488ff583ca5be5529cc
584eeefdc8