CI: increase timeout for server resize confirmation

double the timeout from 5 to 10 seconds.
this should prevent errors like these:

https://zuul.opendev.org/t/openstack/build/547464fe844e4e8ba34faac33f615c92/log/primary/logs/ansible/test-core-openstack#1210



Change-Id: I47157973a8152154a264cc1914b6d2b55bc08cd1
Signed-off-by: Sven Kieske <kieske@osism.tech>

tests/test-core-openstack.sh

@@ -206,7 +206,7 @@ function resize_instance {
             openstack --debug server show ${name}
             return 1
         fi
-        sleep 1
+        sleep 2
     done
 }