SSL_write may return error indicating blocking until all given data
are written.  Because of this, it is preferable to update
last_write_time_ after SSL_write regardless of its return value.

There is no application level failure in h1 upstream.  For h2, SPDY
upstreams, don't call DIE(), instead return -1 to delete handler.

.. so that we can avoid the problem that request_start_time_ is 0

small text fixes

This change adds SPDY upstream tests.

Also HTTP/1 frontend testing method was added.