qubes-lvm: drop unused lvm_image_changed function
qubes-lvm: drop unused lvm_image_changed function

It tries to parse (untrusted) volume content, so remove it to not use it
accidentally.

QubesOS/qubes-issues#2256

woju/qubes-core-admin,QubesOS/qubes-core-admin,woju/qubes-core-admin,woju/qubes-core-admin,marmarek/qubes-core-admin,QubesOS/qubes-core-admin,marmarek/qubes-core-admin,woju/qubes-core-admin,QubesOS/qubes-core-admin,marmarek/qubes-core-admin