Fixed SELinux check

- `grep -i -- SELINUX=#{escape(mode)} /etc/selinux/config` is hit.

`be_disabled `

```
#SELINUX=disabled
SELINUX=enforcing
```

```
SELINUX=disableddddd
```

`grep -i -- ^SELINUX=#{escape(mode)}$ /etc/selinux/config` would better.