Make UpgradeLevelNovaCompute parameters consistent

There is logic in nova-base.yaml that depends on the default for
this parameter being '', and the nova-compute service only needs it
set to auto during upgrade.  That will be done by [1] anyway, so it
doesn't matter what the default is.  It's also not clear to me that
the nova-compute task is even needed now that we're post-Ocata, but
that's not a change I feel comfortable making.

1: https://github.com/openstack/tripleo-heat-templates/blob/master/environments/major-upgrade-composable-steps.yaml

Change-Id: Iccfcb5b68e406db1b942375803cfedbb929b4307
Partial-Bug: 1700664

puppet/services/nova-compute.yaml

@@ -97,7 +97,7 @@ parameters:
   UpgradeLevelNovaCompute:
     type: string
     description: Nova Compute upgrade level
-    default: auto
+    default: ''
   MigrationSshKey:
     type: json
     description: >

puppet/services/nova-conductor.yaml

@@ -45,7 +45,7 @@ parameters:
   UpgradeLevelNovaCompute:
     type: string
     description: Nova Compute upgrade level
-    default: auto
+    default: ''
 
 conditions:
   nova_workers_zero: {equals : [{get_param: NovaWorkers}, 0]}

tools/yaml-validate.py

@@ -75,7 +75,6 @@ PARAMETER_DEFINITION_EXCLUSIONS = {'ManagementNetCidr': ['default'],
                                    'NeutronBigswitchLLDPEnabled': ['default'],
                                    'NeutronWorkers': ['description'],
                                    'ServerMetadata': ['description'],
-                                   'UpgradeLevelNovaCompute': ['default'],
                                    'server': ['description'],
                                    'servers': ['description'],
                                    'ExtraConfig': ['description'],