Fix RAUC tryboot handler set-state idempotency, add more checks (#3891)

When RPi is booted in the tryboot state and the set-state operation is called
for the second time, the tryboot files don't exists anymore and the handler
exits with an error code, printing an error in the Supervisor logs. Fix
handling of this case and add few more checks to make the handler a bit more
robust/traceable.

buildroot-external/board/raspberrypi/rpi5-64/rootfs-overlay/usr/lib/rauc/rpi-tryboot.sh

@@ -73,9 +73,8 @@ case "$1" in
         slot_bootname="$2"
         new_state="$3"
         echo "tryboot set-state $slot_bootname $new_state" >&2
-        if [ "${new_state}" = "good" ]; then
-            touch "${boot_dir}/slot-${slot_bootname}/.good"
-        else
+
+        if [ "${new_state}" != "good" ]; then
             rm -f "${boot_dir}/slot-${slot_bootname}/.good"
             exit 0
         fi
@@ -85,6 +84,20 @@ case "$1" in
 
         # Check if tryboot is active
         if ! cmp -s -n 4 /proc/device-tree/chosen/bootloader/tryboot /dev/zero; then
+            if [ ! -f "${boot_dir}/cmdline-tryboot.txt" ]; then
+                if [ -f "${boot_dir}/slot-${slot_bootname}/.good" ]; then
+                    # Most probably already handled on this boot before, do nothing
+                    exit 0
+                else
+                    echo "cmdline-tryboot.txt not found, can't commit current state." >&2
+                    exit 1
+                fi
+            fi
+            # tryboot.txt MUST exist at this point
+            if [ ! -f "${boot_dir}/tryboot.txt" ]; then
+                echo "tryboot.txt not found, can't commit current state." >&2
+                exit 1
+            fi
             cmdline_tryboot=$(head -n1 "${boot_dir}/cmdline-tryboot.txt")
             tryboot_slot=$(get_value rauc.slot "${cmdline_tryboot}")
             if [ "${tryboot_slot}" != "${slot_bootname}" ]; then
@@ -98,6 +111,10 @@ case "$1" in
             rm "${boot_dir}/tryboot.txt"
             rm /run/systemd/reboot-param
         fi
+
+        if [ "${new_state}" = "good" ]; then
+            touch "${boot_dir}/slot-${slot_bootname}/.good"
+        fi
         ;;
 
     get-current)