Inform user before long trim operation

Trimming huge TemplateVMs or StandaloneVMs could take a lot of time
during update procedure. This might confuse user and imply that the
update operation has hanged. Show a message before performing the trim
operation.

Author: alimirjamali

qubes-rpc/post-install.d/95-fstrim.sh

@@ -5,5 +5,6 @@
 # only run if storage is persistent
 if [ -f /run/qubes/persistent-full ]
 then
+    echo "Trimming qube storage. This may take some time..."
     fstrim -av
 fi