lbuild does not install the kernel source in the standard RHEL7 location.
RHEL's kmodtool (starting in RHEL7) expects the source to be in the standard
location, and when it fails to find it it adds an extra $arch onto the end
of verrel.  With lbuild, verrel already contains the arch, so we change the
kmodtool script so that it does not add another.

--- old/kmodtool	2016-06-07 14:36:20.810907740 -0700
+++ new/kmodtool	2016-06-07 14:37:55.335652424 -0700
@@ -62,7 +62,7 @@ get_kernel_release ()
   local versuffix=${verrel#$verprefix}
   verrel=$(ls -Ud /usr/src/kernels/$verprefix*$versuffix.$arch | sort -V | tail -n 1)
   verrel=${verrel##*/}
-  [[ -z $verrel ]] && verrel=$1.$arch
+  [[ -z $verrel ]] && verrel=$1
   echo "$verrel"
 }