Shutdown JVM on file descriptor exhaustion

patch by jmckenzie, reviewed by marcuse for CASSANDRA-7579
Merge branch 'cassandra-2.1' into trunk

Conflicts:
	src/java/org/apache/cassandra/cli/CliClient.java
	src/java/org/apache/cassandra/cli/CliMain.java
	src/java/org/apache/cassandra/cli/CliSessionState.java
	src/java/org/apache/cassandra/config/DatabaseDescriptor.java
	src/java/org/apache/cassandra/db/compaction/AbstractCompactionStrategy.java
fix error from merge