ssh: improve the logic for detecting blocking direction

This fixes a regression introduced by commit 0feeab78 limiting the speed
of SCP upload to 16384 B/s on a fast connection (such as localhost).
curl: rename --bearer to --oauth2-bearer

The option '--bearer' might be slightly ambiguous in name. It doesn't
create any conflict that I am aware of at the moment, however, OAUTH v2
is not the only authentication mechanism which uses "bearer" tokens.

Reported-by: Kyle L. Huff
URL: http://curl.haxx.se/mail/lib-2013-10/0064.html