The glibc ones (intentionally) cannot handle ptys opened in a
devpts not mounted at /dev/pts.

Drop the (un-exported, unused) virFileOpenTtyAt.
Signed-off-by: NSerge Hallyn <serge.hallyn@canonical.com>
Signed-off-by: NEric Blake <eblake@redhat.com>
(cherry picked from commit 80710c69)

Conflicts:

	src/lxc/lxc_controller.c