Disable random ram directories to prevent OOM during tests.

We need to find a way to enable this without adding crazy heaps etc.
Maybe only selected tests can run this.
If there is an exception that indicates that the shard isn't available then the exception should bubble up to the TransportShardSingleOperationAction class, so the shard level request can be retried on a different shard. (multi term vector api)
Don't wrap the exception in an ElasticSearchException when shard isn't available.
If there is an exception that indicates that the shard isn't available then the exception should bubble up to the TransportShardSingleOperationAction class, so the shard level request can be retried on a different shard. (multi get api)
Added acknowledgment timeout test to OpenCloseIndexTests
Delete Template: When deleting with * and no templates exists, don't 404
closes #3723
improve logging on before/after shared cluster tests
Fix formatting of the documentation.

Remaining '@'s have been replaced with '`'s.
Removed wrong assertion from OpenCloseIndexTests

If a request hasn't been acknowledged, there's no guarantee for any node to hold the up-to-date cluster state (not even the master yet, as the execution is asynchronous)
improve failure message when timing out on green/yellow
call ensureGreen() to get more meaningful debug output on failure
GetActionTests: call ensureGreen() to get more meaningful debug output on failure
call ensureGreen instead of explicit call