Use ES index prefix on deflector, fixes #489

(cherry picked from commit 84813ab619e8dba994e3cdc5b4eafd3ae75c908e)

Conflicts:
	graylog2-server/src/main/java/org/graylog2/indexer/Deflector.java
	graylog2-server/src/main/java/org/graylog2/indexer/healing/FixDeflectorByDeleteJob.java
	graylog2-server/src/main/java/org/graylog2/indexer/healing/FixDeflectorByMoveJob.java
	graylog2-server/src/main/java/org/graylog2/periodical/DeflectorManagerThread.java