ACCUMULO-2512 Wait for each MAC process to exit before returning from MAC.stop()
Merge branch '1.4.5-SNAPSHOT' into 1.5.2-SNAPSHOT

Conflicts:
	minicluster/src/main/java/org/apache/accumulo/minicluster/MiniAccumuloCluster.java
Merge branch '1.5.2-SNAPSHOT' into 1.6.0-SNAPSHOT

Conflicts:
	minicluster/src/main/java/org/apache/accumulo/minicluster/MiniAccumuloCluster.java