arguments: remove trailing slashes for the input lxcpath

In lxc_cmd(), we use
snprintf(path, len, "%s/%s/command", lxcpath ? lxcpath : inpath, name);
to fill sock name, this assume lxcpath have no trailing slashes, so
if we use
lxc-info -n test -P /usr/local/var/lib/lxc_anon/
to get a running container's state, we will get state: STOPPED which
is wrong, because we combine a wrong sock name.

To fix this, just remove trailing slashes when parsing arguments.

Signed-off-by: Qiang Huang <h.huangqiang@huawei.com>
Acked-by: Serge Hallyn <serge.hallyn@ubuntu.com>
Signed-off-by: Serge Hallyn <serge.hallyn@ubuntu.com>
utils: move remove_trailing_slashes to utils

Signed-off-by: Qiang Huang <h.huangqiang@huawei.com>
Acked-by: Serge Hallyn <serge.hallyn@ubuntu.com>
Signed-off-by: Serge Hallyn <serge.hallyn@ubuntu.com>