atomic, cloud: remove rhgb by removing plymouth

a59dfe5 caused us a few problems:
  - sed was breaking the symlink on atomic systems
  - /boot/grub2/grub.cfg is not the right file on a UEFI system
  - etc..

We'll solve this problem a different way by just not installing
plymouth in our systems, which is another way [1] to make sure
rhgb/quiet don't appear on your kernel command line.

[1] ee91db6fa3/pyanaconda/payload/__init__.py (L722-L726)

fedora-atomic.ks

@@ -137,7 +137,4 @@ echo "Adding Developer Mode GRUB2 menu item."
 # https://bugs.launchpad.net/cloud-init/+bug/1670052
 truncate -s 0 /etc/resolv.conf
 
-# Disable rhgb/quiet: https://bugzilla.redhat.com/show_bug.cgi?id=510523
-sed -i 's/rhgb quiet//' /boot/grub2/grub.cfg
-
 %end

fedora-cloud-base.ks

@@ -81,6 +81,9 @@ which
 #-kbd
 -uboot-tools
 -kernel
+# No need for plymouth. Also means anaconda won't put rhgb/quiet
+# on kernel command line
+-plymouth
 
 %end
 
@@ -259,8 +262,5 @@ touch /etc/machine-id
 # https://bugs.launchpad.net/cloud-init/+bug/1670052
 truncate -s 0 /etc/resolv.conf
 
-# Disable rhgb/quiet: https://bugzilla.redhat.com/show_bug.cgi?id=510523
-sed -i 's/rhgb quiet//' /boot/grub2/grub.cfg
-
 %end