infest prepare: drop support for CentOS 6

krebs/4lib/infest/prepare.sh

@@ -14,10 +14,6 @@ prepare() {(
         ;;
       centos)
         case $VERSION_ID in
-          6)
-            prepare_centos "$@"
-            exit
-            ;;
           7)
             prepare_centos "$@"
             exit
@@ -51,13 +47,6 @@ prepare() {(
         esac
         ;;
     esac
-  elif test -e /etc/centos-release; then
-    case $(cat /etc/centos-release) in
-      'CentOS release 6.5 (Final)')
-        prepare_centos "$@"
-        exit
-        ;;
-    esac
   fi
   echo "$0 prepare: unknown OS" >&2
   exit -1