Fix checking vps_is_mounted() return value

vps_is_mounted() does not return boolean value, as it can return -1 in
case of an error. Therefore, we should not treat it as such.

Document vps_is_mounted() return values, and replace all places
using this function as follows:

	if (vps_is_mounted())	-> if (vps_is_mounted() == 1)

	if (!vps_is_mounted())	-> if (vps_is_mounted() == 0)

We still don't do any error processing, but it is already way better
than to assume that CT is mounted while in fact we have an error.

Should also fix https://bugzilla.openvz.org/2534

Reported-by: Konstantin Pavlov <thresh@altlinux.org>
Signed-off-by: Kir Kolyshkin <kir@openvz.org>
9 files changed