Add wait_for_port and wait_for_log systemd unit logic

[guidograzioli]

New parameters allow to wait for healthy status in the systemd unit:

Variable	Description	Default
keycloak_quarkus_systemd_wait_for_port	Whether systemd unit should wait for keycloak port before returning	{{ keycloak_quarkus_ha_enabled }}
keycloak_quarkus_systemd_wait_for_log	Whether systemd unit should wait for service to be up in logs	false
keycloak_quarkus_systemd_wait_for_timeout	How long to wait for service to be alive (seconds)	60
keycloak_quarkus_systemd_wait_for_delay	Activation delay for service systemd unit (seconds)	10

Both keycloak_quarkus_systemd_wait_for_port and keycloak_quarkus_systemd_wait_for_log can be active at the same time, but mind they will be executed post-exec in serial, potentially adding up to the startup time.

Part of #182

[rpelisse]

Misc comments, otherwise looks good to me.