Handle non-integer values for if-delete-at

If a client passes us a non-integer value for if-delete-at we'll now
properly report a 400 error instead of a 503.

Closes-Bug: 1259300
Change-Id: I8bb0bb9aa158d415d4f491b5802048f0cd4d8ef6
Just trying to keep /tmp clean

Change-Id: Ia8d7cf37a4f6a4652cb3440a896cefb411cdb41a
update ssync tests to use req.get_response()

Change-Id: I2fa752b42669fab27d1a8e7562d52d8f8b848351
Merge "Just trying to keep /tmp clean"