multinode tests: Use the correct container in multinode_sbctl().

Commit e64a15e ("Modified the CI to use ovn-fake-multinode v0.3.")
changed the ovn-fake-multinode version that's used by our multinode
tests.  In the new version default container names are slightly
different.  When I applied 3baa8c6 ("multinode tests:
Simplify/Cleanup migration test.") I didn't take that into account
during the rebase.

This commit fixes the multinode_sbctl() implementation.

Fixes: 3baa8c6 ("multinode tests: Simplify/Cleanup migration test.")
Signed-off-by: Dumitru Ceara <dceara@redhat.com>
Acked-by: Xavier Simonart <xsimonar@redhat.com>

Author: dceara

tests/multinode-macros.at

@@ -94,7 +94,7 @@ multinode_nbctl () {
 }
 
 multinode_sbctl () {
-    m_as ovn-central-az1-1 ovn-sbctl "$@"
+    m_as ovn-central-az1 ovn-sbctl "$@"
 }
 
 check_fake_multinode_setup_by_nodes() {