Add test for streaming timeout message

Fix streaming tests (stream param was not passes, was streaming the
inmemory index results)
Update test for 503 error response
Fix alt error msg from 2i timeout

The code could receive two different error messages depending on where
the 2i timeout occurred (webmachine process vs in the index FSM). Some
extra error handling code in the streaming requests was added since it
was useful when figuring out this bug.
Merge pull request #369 from basho/eas-1.4.2-2i-timeout-fix

Eas 1.4.2 2i timeout fix