Fixed NPE in recovery api by serializing the recovery type in StartRecoveryRequest.

Closes #6190
[TEST] Verify that all pending tasks are rely executed on *all* nodes.
[TEST] Set the local flag to execute on all nodes
Merge branch '1.2' of https://github.com/elasticsearch/elasticsearch into issue6441
Revert "Apply @bleskes patch and test fix"

This reverts commit 62426971ce5e769fe5d1998b28e4ef4d12d71870.
Apply @bleskes new patch
add missing file