Don't use jsonpath_ng in the monitor loop

Each jsonpath expression usage cause a storm of fstat() for no good reason.
As the monitor loop is ran frequently, optimize that by not using jsonpath.

Anyway, jsonpath was just a dev convenience here. Did nothing tricky to do
without this lib.

lib/osvcd_mon.py

@@ -27,7 +27,6 @@
                         list_services, svc_pathcf, fmt_path, \
                         resolve_path, factory
 from freezer import Freezer
-from jsonpath_ng import jsonpath, parse
 
 STARTED_STATES = [
     "n/a",
@@ -2140,12 +2139,17 @@ def service_started_instances_count(self, path):
         """
         Count the number of service instances in 'started' local expect state.
         """
-        jsonpath_expr = parse("*.services.status.'%s'.monitor.local_expect" % path)
+        count = 0
         try:
-            count = len([True for match in jsonpath_expr.find(shared.CLUSTER_DATA) if match.value == "started"])
+            for node, ndata in shared.CLUSTER_DATA.items():
+                try:
+                    local_expect = ndata["services"]["status"][path]["monitor"]["local_expect"]
+                except Exception:
+                    continue
+                if local_expect == "started":
+                    count += 1
             return count
         except Exception as exc:
-            self.log.warning(exc)
             return 0
 
     def up_service_instances(self, path):