kernel-install: restore priority of check for /boot/loader/entries

kernel-install: restore priority of check for /boot/loader/entries

Before 9e82a74cb0f08a288f9db228a0b5bec8a7188cdb, we had a check like the
following:

if [[ -d /efi/loader/entries ]] || [[ -d /efi/$MACHINE_ID ]]; then
    ENTRY_DIR_ABS="/efi/$MACHINE_ID/$KERNEL_VERSION"
elif [[ -d /boot/loader/entries ]] || [[ -d /boot/$MACHINE_ID ]]; then
    ENTRY_DIR_ABS="/boot/$MACHINE_ID/$KERNEL_VERSION"
elif [[ -d /boot/efi/loader/entries ]] || [[ -d /boot/efi/$MACHINE_ID ]]; then
    ENTRY_DIR_ABS="/boot/efi/$MACHINE_ID/$KERNEL_VERSION"
…

In stock Fedora 34-, /efi isn't used, but grub creates /boot/loader/entries and
installs kernels and initrds directly in /boot. Thus the second arm of the
check wins, and we end up with BOOT_ROOT=/boot.

After 9e82a74cb0f08a288f9db228a0b5bec8a7188cdb, we iterate over the inner
directory first and over the second directory later:

[ -d /efi/<machine-id> ]
[ -d /boot/efi/<machine-id> ]
[ -d /boot/<machine-id> ]
[ -d /efi/Default ]
[ -d /boot/efi/Default ]
[ -d /boot/Default ]
[ -d /efi/loader/entries ]
[ -d /boot/efi/loader/entries ]
[ -d /boot/loader/entries ]

This was partially reverted by 447a822f8ee47b63a4cae00423c4d407bfa5e516 which
removed Default from the list, and a5307e173bf86d695fe85b8e15e91126e8618a14,
which moved checks for /boot up, so we ended up with:

[ -d /efi/<machine-id> ]
[ -d /boot/<machine-id> ]
[ -d /boot/efi/<machine-id> ]
[ -d /efi/loader/entries ]
[ -d /boot/loader/entries ]
[ -d /boot/efi/loader/entries ]

6637cf9db67237857279262d93ee0e39023c5b85 added autodetection of an entry
token, so we end up checking the following suffixes:

<machine-id>, $IMAGE_ID, $ID, Default

But the important unchanged characteristic is that we iterate over the suffix
first. Sadly this breaks Fedora, because we find /boot/efi/<machine-id> before
we could find /boot/loader/entries. It seems that every possible aspect of
behaviour matters for somebody, so we need to keep the original order of
detection.

With the patch:

[ -d /efi/<machine-id> ]
...
[ -d /efi/loader/entries ]
[ -d /boot/<machine-id> ]
...
[ -d /boot/loader/entries ]
[ -d /boot/efi/<machine-id> ]
...
[ -d /boot/efi/loader/entries ]

Note that we need to check for "loader/entries" too, even though it is not
an entry-token candidate, so that we get the same detection priority as
before.

Fixes https://bugzilla.redhat.com/show_bug.cgi?id=2071034.