Switch ARM64 testing to bullseye

This more closely matches the nodepool-builder container, which is
Bullseye based.

Refactor to remove unnecessary abstract job.

Change-Id: I34822608f19e1ce9ef781034ff831d6359ed8e15

.zuul.d/jobs.yaml

@@ -38,22 +38,16 @@
     name: dib-functests-arm64
     description: |
       ARM64 build tests
-    abstract: true
+    nodeset: debian-bullseye-arm64
     parent: dib-functests-base
     vars:
       dib_functests:
         - ubuntu-minimal/bionic-arm64-build-succeeds
         - ubuntu-minimal/focal-arm64-build-succeeds
         - centos-minimal/8-aarch64-build-succeeds
-        - openeuler-minimal/20.03-LTS-SP2-build-succeeds
-
-# ARM64 tests
-- job:
-    name: dib-functests-arm64-bionic
-    description: |
-      ARM64 image tests building on am ARM64 Bionic host
-    nodeset: ubuntu-bionic-arm64
-    parent: dib-functests-arm64
+        # NOTE(ianw) 2021-10-15 : this currently segfaults
+        # yum...
+        #- openeuler-minimal/20.03-LTS-SP2-build-succeeds
 
 #
 # Build and boot functional tests

.zuul.d/project.yaml

@@ -37,7 +37,7 @@
             voting: false
     check-arm64:
       jobs:
-        - dib-functests-arm64-bionic
+        - dib-functests-arm64
     gate:
       jobs:
         - openstack-tox-pylint