ssh: unban the use of pipe character in user@host:port string
This vulnerability was fixed by the previous patch and there were more ways
to exploit than using '|shellcmd'. So it doesn't make sense to reject only
pipe character.
Test cases are updated to actually try to exploit the bug. As the SSH bridge
of git/svn subrepos are not managed by our code, the tests for non-hg subrepos
are just removed.
This may be folded into the original patches.