Fix rfpkg build for el7
    
    For reason template for epel miss some variables when we have "%define buildforkernels current"
    without this patch we can see the error on el7 of kmod-VirtualBox
    
    rfpkg build
    error: line 73: %package       -n kmod-VirtualBox
    : package kmod-VirtualBox already exists
    error: query of specfile /home/sergio/rpmfusion/new/VirtualBox-kmod/VirtualBox-kmod.spec failed, can't parse
    
    Could not get n-v-r-e from /home/sergio/rpmfusion/new/VirtualBox-kmod/VirtualBox-kmod.spec
    Note: You can skip NVR construction & NVR check with --skip-nvr-check. See help for more info.
    Could not execute build: Cannot continue without properly constructed NVR.