utils_selinux: Add two helper function in utils_selinux.

Add two funtions is_enforcing() and is_permissive().

Signed-off-by: Dongsheng Yang <yangds.fnst@cn.fujitsu.com>
utils_misc: Change the selinux_enforcing as a deprecated function.

Signed-off-by: Dongsheng Yang <yangds.fnst@cn.fujitsu.com>
virttest: treewide, replace calling of selinux_enforcing with is_enforcing.

Signed-off-by: Dongsheng Yang <yangds.fnst@cn.fujitsu.com>
Merge pull request #1696 from yangdongsheng/selinux

utils_selinux: Add two helper function in utils_selinux.