Add logging about not autobootstrapping a seed.

Patch by brandonwilliams for CASSANDRA-6972
Merge branch 'cassandra-1.2' into cassandra-2.0

Conflicts:
	src/java/org/apache/cassandra/service/StorageService.java
Fix LatencyMetrics returning infinity.

Patch by Nick Bailey, reviewed by Lyuben Todorov for CASSANDRA-6920
Merge branch 'cassandra-1.2' into cassandra-2.0
Fix LatencyMetrics returning infinity.

Patch by Nick Bailey, reviewed by Lyuben Todorov for CASSANDRA-6920