[CI] Unblock CI by fixing job regex and non-voting snmp

Two issues have occcured:

1) Zuul has decided some syntax is deprecated and generates an error.
   The exlcusionary nature of the syntax is just not supported by RE2
   which is the new requirement, so explicitly matching "^master$"
   as opposed to "not stable branches".

2) Marking the snmp job as non-voting, the root issue appears to be ipxe
or the VMs, unknown as of yet.

Change-Id: I68aa95eb1ed80a0fde1c29d708ebd606393481aa

zuul.d/ironic-jobs.yaml

@@ -696,7 +696,7 @@
     vars:
       tox_envlist: py3
     # The job only tests the latest and shouldn't be run on the stable branches
-    branches: ^(?!stable)
+    branches: ^master$
     required-projects:
       - name: github.com/sqlalchemy/sqlalchemy
         override-checkout: main

zuul.d/project.yaml

@@ -26,7 +26,10 @@
         - ironic-standalone-redfish
         - ironic-tempest-bios-redfish-pxe
         - ironic-tempest-uefi-redfish-vmedia
-        - ironic-tempest-wholedisk-bios-snmp-pxe
+        # NOTE(TheJulia): Moving to not-voting due to bug
+        # https://bugs.launchpad.net/ironic/+bug/2034588
+        - ironic-tempest-wholedisk-bios-snmp-pxe:
+            voting: false
         - ironic-tempest-partition-uefi-ipmi-pxe
         # NOTE(TheJulia) Marking multinode non-voting on 20210311
         # Due to a high failure rate on limestone where the compute1
@@ -79,7 +82,9 @@
         - ironic-standalone-redfish
         - ironic-tempest-bios-redfish-pxe
         - ironic-tempest-uefi-redfish-vmedia
-        - ironic-tempest-wholedisk-bios-snmp-pxe
+        # NOTE(stevebaker): Disabled due to bug
+        # https://bugs.launchpad.net/ironic/+bug/2034588
+        # - ironic-tempest-wholedisk-bios-snmp-pxe
         - ironic-tempest-partition-uefi-ipmi-pxe
         # NOTE(TheJulia): Disabled multinode on 20210311 due to Limestone
         # seeming to be