Provide ha-policy implementation

[guidograzioli]

Comprehensive change that provides configuration for the ha-policy element in broker.xml.

Before the change, ha cluster would default to live-only role which in case of shared store would form clusters of live server waiting to obtain the master lock. That configuration remains the default for the new variable:

Variable	Description	Default
activemq_ha_role	Instance role for high availability	live-only

The value can be set to live-only (masters only), master or slave (shared storage master/slave), or replicated or replicate (replication master/slave).

Two more variables are added to configure the systemd startup checks:

Variable	Description	Default
activemq_systemd_wait_for_timeout	How long to wait for service to be alive (seconds)	60
activemq_systemd_wait_for_delay	Activation delay for service systemd unit	10

Finally, this change contains a fix that wouldn't apply settings for max-hops and lb_policy in cluster-connections.