Merge pull request #1540 from darkworks/darkworks-yum_check

check for yum properly.

bin/v-update-sys-vesta

@@ -33,7 +33,7 @@ check_args '1' "$#" 'PACKAGE'
 #                       Action                             #
 #----------------------------------------------------------#
 
-if [ -d "/etc/sysconfig" ]; then
+if [ -n "$(command -v yum)" ]; then
     # Clean yum chache
     yum -q clean all