ACCUMULO-2332 Rework how address parsing is currently done by the GC.

Try to reduce the number of creations of an InetSocketAddress and ensure
that an externally addressable hostname/address is placed in zookeeper.
Also, replace 0.0.0.0 with the hostname for the machine when provided
as the address
Merge branch '1.5.1-SNAPSHOT' into 1.6.0-SNAPSHOT

Conflicts:
	server/src/main/java/org/apache/accumulo/server/gc/SimpleGarbageCollector.java
Merge branch '1.6.0-SNAPSHOT'
ACCUMULO-2329 Infer the GC role from master when gc file is not present.
Merge branch '1.5.1-SNAPSHOT' into 1.6.0-SNAPSHOT
Merge branch '1.6.0-SNAPSHOT'