CLOUDSTACK-8003: test_egress_fw_rules.py - Remove test case dependency on each other and improve cleanup code

Signed-off-by: SrikanteswaraRao Talluri <talluri@apache.org>
CLOUDSTACK-8002: test_high_availability.py - Skip test cases if enough hosts are not available

Signed-off-by: SrikanteswaraRao Talluri <talluri@apache.org>