workaround out of memory error on loop ubuntu iso

ks-trans.cfg

@@ -136,6 +136,8 @@ if [ "$distro" = "ubuntu" ]; then
     cat <<EOF >$grub_cfg
         set timeout=5
         menuentry "reinstall" {
+            # https://bugs.launchpad.net/ubuntu/+source/grub2/+bug/1851311
+            rmmod tpm
             search --no-floppy --label --set=root installer
             loopback loop $iso_file
             linux (loop)/casper/vmlinuz iso-scan/filename=$iso_file autoinstall cloud-config-url=$ks $extra_cmdline ---