Partial revert "Bug: Fix order of 'arakoon_multi_get' result"

After further investigation, it turned out the client libraries didn't
contain bugs, but the Arakoon 'multi_get' result wire format was
changed by accident in the 1.6 cycle.

This commit reverts the change to the 'arakoon_multi_get'
implementation in order to restore the original decoding mechanism
(compatible with Arakoon < 1.6 and >= 1.7), but retains the validation
code in the tests added by d3ed4069c9.

This reverts part of commit d3ed4069c9eb13c2c6d8ab99c54fc790db286405.

See: ARAKOON-436
See: http://jira.incubaid.com/browse/ARAKOON-436
See: d3ed4069c9eb13c2c6d8ab99c54fc790db286405
Change-Id: I91904ff29096dd5ee181f4a1a2e4757413df83d8