Values:
HEALTH_CHECK_FIREWALL_STATE_UNSPECIFIED (0):
State is unspecified. Default state if not
populated.
CONFIGURED (1):
There are configured firewall rules to allow
health check probes to the backend.
MISCONFIGURED (2):
There are firewall rules configured to allow
partial health check ranges or block all health
check ranges. If a health check probe is sent
from denied IP ranges, the health check to the
backend will fail. Then, the backend will be
marked unhealthy and will not receive traffic
sent to the load balancer.