RedHat: support building on ELRepo kernels

Amend the pattern matching in openafs-kmodtool to support
building for kernels from ELRepo.

Change-Id: I1264490bee90fadfd24d5cd04ea87df4f9c8924d
Reviewed-on: http://gerrit.openafs.org/10083
Tested-by: BuildBot <buildbot@rampaginggeek.com>
Reviewed-by: Derrick Brashear <shadow@your-file-system.com>