Fixing function name to follow standards

The current style guide is for functions implemented as xx-xx
to be named xx_xx in the python code.  The functionality implementing
the claim build plugin has been implemented as claim-build, thus
the function in the python code should be claim_build
instead of claimbuild as it is currently implemented

Change-Id: I0cc3ebe37bfd6249f2985f0208697d6cc1a275db
Reviewed-on: https://review.openstack.org/18688
Reviewed-by: Clark Boylan <clark.boylan@gmail.com>
Approved: James E. Blair <corvus@inaugust.com>
Reviewed-by: James E. Blair <corvus@inaugust.com>
Tested-by: Jenkins