Switch agent report_interval option to float

Being able to set report_interval > 0 and < 1 makes
it easier to consistently reproduce rpc race
conditions.

Change-Id: I4d907159147177e98b043e7e800aea5cf8c23103
Related-Bug: #1224001

neutron/agent/common/config.py

@@ -32,8 +32,8 @@
 ]
 
 AGENT_STATE_OPTS = [
-    cfg.IntOpt('report_interval', default=4,
-               help=_('Seconds between nodes reporting state to server')),
+    cfg.FloatOpt('report_interval', default=4,
+                 help=_('Seconds between nodes reporting state to server')),
 ]