Adding check for null (indicating an interrupted take), retrying then.

(cherry picked from commit f6fee85a6a59d473ebeb8f00e642534021d5cbb7)
(cherry picked from commit 2ebc2e7426a56f9c38f238e09dc6706d54b489f7)
Messed up the null check by not using the local variable afterwards.

(cherry picked from commit c2e132dce5ed182218d302f5cd89a499e39b9982)
(cherry picked from commit 6942fcffbdaadc4e70641b116882c643a00444d7)
Making pop from DiskJournalCache block if queue is empty.

(cherry picked from commit af4d07753838fde9e9a9fb0b6a1a4d09a6c15997)
(cherry picked from commit 8d4ea55cc88e57076dfd1a39fe0816d00bbecdee)
Formatting AMQP vhost and routing key strings to allow parallelism.

(cherry picked from commit 37d0a5864b132af645e003e6d4f2b46c5a415499)
(cherry picked from commit 4e845a5e14a47692b9bbf437364ee6e08c65d802)

Conflicts:
	graylog2-radio/src/main/java/org/graylog2/radio/transports/amqp/AMQPProducer.java
Correcting superfluous ,