Because of the way unseal-hotp is called from gui-init,
dropping to a recovery shell when failing to mount /boot
causes it to hang, leaving the user stranded until they
kill it with CTRL+C. Instead, simply return and continue
to the main GUI menu where the user can address the problem.
Rename the function to clarify difference from other versions
of mount_boot() which do drop to the recovery shell.
Signed-off-by: Matt DeVillier <matt.devillier@puri.sm>