Disable resize tests in Tempest if using cells with custom flavors

By default, devstack creates it's own test flavors for Tempest runs.

These are not in the cells API database since they are non-default
for nova so any resize tests in Tempest with cells and these custom
flavors fail.

Configure Tempest to not run resize tests if using cells and custom
flavors.

This allows us to also clean up a bunch of the resize skips found
in nova/devstack/tempest-dsvm-cells-rc.

Change-Id: I20f46024e45e32c60275703a193a56ae8cfe7eca
Closes-Bug: #1513925
diff --git a/lib/tempest b/lib/tempest
index 32630db..691ad86 100644
--- a/lib/tempest
+++ b/lib/tempest
@@ -377,6 +377,15 @@
         iniset $TEMPEST_CONFIG compute-feature-enabled shelve False
         # Cells doesn't support hot-plugging virtual interfaces.
         iniset $TEMPEST_CONFIG compute-feature-enabled interface_attach False
+
+        if  [[ -z "$DEFAULT_INSTANCE_TYPE" ]]; then
+            # Cells supports resize but does not currently work with devstack
+            # because of the custom flavors created for Tempest runs which are
+            # not in the cells database.
+            # TODO(mriedem): work on adding a nova-manage command to sync
+            # flavors into the cells database.
+            iniset $TEMPEST_CONFIG compute-feature-enabled resize False
+        fi
     fi
 
     # Network