kpatch: add yet another core module path

Ok, the number of valid locations for the core module is a getting
ridiculous.  But on RHEL I'm seeing issues with installing the core
module in the "extra" path.  On the next depmod run, it gets added to
modules.dep, and on a subsequent kpatch install I see the following
errors:
```
    /usr/lib/dracut/modules.d/50drm/module-setup.sh: line 26: /lib/modules/3.10.0-123.4.4.el7.x86_64//weak-updates/kpatch/kpatch.ko: No such file or directory
    /usr/lib/dracut/modules.d/90kernel-modules/module-setup.sh: line 14: /lib/modules/3.10.0-123.4.4.el7.x86_64//weak-updates/kpatch/kpatch.ko: No such file or directory
    modinfo: ERROR: Module /lib/modules/3.10.0-123.4.4.el7.x86_64/weak-updates/kpatch/kpatch.ko not found.
```
Until the core module gets merged into Linux, I think we can put it in
/usr/lib/kpatch, which is also where the patch modules are going to be
installed in RHEL.

Leaving the other options available for now, so as to not break
contrib/kpatch.spec, and to leave our options open.