Do not hard code the current Descriptor version into BootstrapTest.
patch by jasobrown; reviewed by Aleksey Yeschenko for CASSANDRA-5495
Merge branch 'cassandra-1.2' into trunk

Conflicts:
	src/java/org/apache/cassandra/io/sstable/Descriptor.java
	test/unit/org/apache/cassandra/streaming/BootstrapTest.java