handle the case where source is rpm (needs to have 'base/' prepended)

cherry-picked from the master branch by adamhl

manifests/rpm.pp

@@ -4,7 +4,7 @@
 # base::rpm::yumrepo definition
 #
 # namevar must match source file name
-define base::rpm::yumrepo ($source='rpm') {
+define base::rpm::yumrepo ($source='base/rpm') {
   file { "/etc/yum.repos.d/${name}":
     source  => "puppet:///modules/${source}/${name}",
     require => [ Package['yum'], File['/etc/yum.repos.d'] ]