Consider pre-existing VMs when testing server list

When running the test_list_servers_by_limits_greater_than_actual_count
test using pre-provisioned accounts, the test gives a false positive
since it does not consider the VMs the user could already have before
the test started.
This commit fixes the test by considering those pre-existing VMs a
user might have.

Change-Id: I5d18cdced9f074d3214f9f0b9515929ba5bf7c04
Closes-Bug: 1592971
1 file changed