dom+vm: Copy dom0 yum.conf to UpdateVM

At least to use dom0 'exclude' options, not VM one. Especially to not exlude
kernel and xorg updates...

common/qubes_check_for_updates.sh

@@ -8,7 +8,7 @@ if ! [ -d "$DOM0_UPDATES_DIR" ]; then
 fi
 
 mkdir -p $DOM0_UPDATES_DIR/etc
-cp /etc/yum.conf $DOM0_UPDATES_DIR/etc/
+sed -i '/^reposdir\s*=/d' $DOM0_UPDATES_DIR/etc/yum.conf
 
 # check also for template updates
 echo "Checking for template updates..." >&2

common/qubes_download_dom0_updates.sh

@@ -34,7 +34,7 @@ if ! [ -d "$DOM0_UPDATES_DIR" ]; then
 fi
 
 mkdir -p $DOM0_UPDATES_DIR/etc
-cp /etc/yum.conf $DOM0_UPDATES_DIR/etc/
+sed -i '/^reposdir\s*=/d' $DOM0_UPDATES_DIR/etc/yum.conf
 
 if [ "x$CLEAN" = "1" ]; then
     yum $OPTS clean all