fix datacenter loop issue with lookup plugins (ansible-collections#547)

SUMMARY
This fixes an issue where the datacenter search filter is never actually set. In some cases this caused the lookup plugin to short circuit and return incorrect results, or return results that were outside of the search scope
ISSUE TYPE

Bugfix Pull Request

COMPONENT NAME
All lookup plugins
ADDITIONAL INFORMATION
Before
    "lookup('vmware.vmware_rest.resource_pool_moid', '/' + vcenter_datacenter + '/' + vcenter_cluster + '/')": [
        "resgroup-3026",
        "resgroup-35",
        "resgroup-5060",
        "resgroup-55921",
        "resgroup-63368"
    ]
}

After
    "lookup('vmware.vmware_rest.resource_pool_moid', '/' + vcenter_datacenter + '/' + vcenter_cluster + '/')": [
        "resgroup-63368"
    ]
}

Reviewed-by: Danielle Barda
Reviewed-by: Anna Savina

changelogs/fragments/547-fix-datacenter-loop-in-lookups.yml

@@ -0,0 +1,3 @@
+---
+bugfixes:
+  - lookup plugins - Fixed issue where datacenter search filter was never properly set

plugins/plugin_utils/lookup.py

@@ -90,6 +90,10 @@ def __init__(self, options, session):
         self.api = VcenterApi(options["vcenter_hostname"], session)
         self.active_filters = {}
         self.object_type = options["object_type"]
+        # this is an internal flag that indicates if we tried to find the datacenter or not
+        # if its true, we stop trying and save some api calls.
+        # see process_intermediate_path_part
+        self._searched_for_datacenter = False
 
     @classmethod
     async def entry_point(cls, terms, options):
@@ -164,12 +168,14 @@ async def process_intermediate_path_part(self, intermediate_object_name):
         Returns:
             str or None, a single MoID or none if nothing was found
         """
-        if not self.active_filters.get("datacenter"):
+        if not self._searched_for_datacenter:
+            self._searched_for_datacenter = True
             result = await self.get_object_moid_by_name_and_type(
                 intermediate_object_name, "datacenter"
             )
-            self.active_filters["datacenters"] = result
-            return result
+            if result:
+                self.active_filters["datacenters"] = result
+                return result
 
         if self.object_type == "vm":
             result = await self.get_object_moid_by_name_and_type(