Minimize the tests footprint in multinode job

multinode job run all the tests including multinode and
non multinode tests. But we do not need to run all the
non multinode tests in this job instead smoke tests along
with multinode tests should be enough to run. This make
multinode jobs to run only smoke and multinode tests. For
that, we need to tag the multinode tests with 'multinode' attr.

Relavant-Bug: #2004780
Change-Id: I7e87d1db3ef3a00b3d27f0904d0af6a270e03837
diff --git a/tox.ini b/tox.ini
index d5b41af..972c05e 100644
--- a/tox.ini
+++ b/tox.ini
@@ -301,6 +301,18 @@
     find . -type f -name "*.pyc" -delete
     tempest run --regex {[testenv:slow]regex} {posargs}
 
+[testenv:multinode]
+envdir = .tox/tempest
+sitepackages = {[tempestenv]sitepackages}
+basepython = {[tempestenv]basepython}
+setenv = {[tempestenv]setenv}
+deps = {[tempestenv]deps}
+# The regex below is used to select the multinode and smoke tagged tests
+regex = '\[.*\bsmoke|multinode\b.*\]'
+commands =
+    find . -type f -name "*.pyc" -delete
+    tempest run --regex {[testenv:multinode]regex} {posargs}
+
 [testenv:ipv6-only]
 envdir = .tox/tempest
 sitepackages = {[tempestenv]sitepackages}