hg-ssh: normalize the drive of the current working directory on windows
For some reason os.getcwd() can return either `c:` or `C:`. We normalize this to
`C:` and the like. This fix `test-ssh-bundle1.t` on windows.
Differential Revision: https://phab.mercurial-scm.org/D11042
#require docutils gettext
$ $TESTDIR/check-gendoc ru
checking for parse errors