Merge branch 'sp/smart-http-content-type-check'

The smart HTTP clients forgot to verify the content-type that comes
back from the server side to make sure that the request is being
handled properly.

* sp/smart-http-content-type-check:
http_request: reset "type" strbuf before adding
t5551: fix expected error output
Verify Content-Type from smart HTTP servers

diff --cc http-push.c
Simple merge