usrmove convert doesn't handle /lib/modules properly

[Bruno Wolff III]

While this won't have too much affect on upgrades from previous releases
to f17/rawhide, it did cause me some puzzlement going from pre usrmove
rawhide to post usrmove rawhide where I run nondebug kernels and needed
to rebuild a third party kernel module to fix a depency change from
usrmove. I found that that build directory (/lib/modules/*/build) contents
didn't get copied over which blocked rebuilding the module until I reinstall
the running kernel. Kernels installed since the conversion do have
a proper build directory, so I expect it is some issue with the
conversion script rather than the directory layout.