Log Prometheus Query

(cherry picked from commit 6c61ea7)
(cherry picked from commit 884a43a)
(cherry picked from commit 572ad44)

Author: priteau

cloudkitty/collector/prometheus.py

@@ -213,6 +213,8 @@ def fetch_all(self, metric_name, start, end, scope_id, q_filter=None):
         if query_suffix:
             query = "{0} {1}".format(query, query_suffix)
 
+        LOG.debug("Calling Prometheus with query: %s", query)
+
         try:
             res = self._conn.get_instant(
                 query,