Improve RAPI detection of the watcher

If the watcher is not allowed to access RAPI, it doesn't mean that it is dead
and needs to be restarted.

Fixes Issue 752.
Signed-off-by: Michele Tartara <mtartara@google.com>
Reviewed-by: Hrvoje Ribicic <riba@google.com>

lib/watcher/__init__.py

@@ -329,6 +329,10 @@ def IsRapiResponding(hostname):
   Connects to RAPI port of hostname and does a simple test. At this time, the
   test is GetVersion.
 
+  If RAPI responds with error code "401 Unauthorized", the test is successful,
+  because the aim of this function is to assess whether RAPI is responding, not
+  if it is accessible.
+
   @type hostname: string
   @param hostname: hostname of the node to connect to.
   @rtype: bool
@@ -344,8 +348,12 @@ def IsRapiResponding(hostname):
     logging.warning("RAPI certificate error: %s", err)
     return False
   except rapi.client.GanetiApiError, err:
-    logging.warning("RAPI error: %s", err)
-    return False
+    if err.code == 401:
+      # Unauthorized, but RAPI is alive and responding
+      return True
+    else:
+      logging.warning("RAPI error: %s", err)
+      return False
   else:
     logging.debug("Reported RAPI version %s", master_version)
     return master_version == constants.RAPI_VERSION