Fix U-Boot environment handling (#1001)

* Use /run as default location for lock files for U-Boot tools

While there is a command line parameter to set the lock file explicitly,
there are other tools invoking fw_setenv (in particular rauc) which do
not set the lock file. Using /run by default makes fw_setenv use the
correct lock file in all situations.

* Don't explicitly set lock file location

Since we patch U-Boot tools to use /run by default setting it explicitly
is unnecessary.

buildroot-external/rootfs-overlay/usr/libexec/hassos-persists

@@ -8,9 +8,9 @@ MACHINE_ID=$(cat /etc/machine-id)
 if [ -e /usr/sbin/fw_setenv ]; then
 
     # machine-id
-    if [ "$(fw_printenv -l /run -n MACHINE_ID)" != "${MACHINE_ID}" ]; then
+    if [ "$(fw_printenv -n MACHINE_ID)" != "${MACHINE_ID}" ]; then
         echo "[INFO] set machine-id to ${MACHINE_ID}"
-        fw_setenv -l /run MACHINE_ID "${MACHINE_ID}"
+        fw_setenv MACHINE_ID "${MACHINE_ID}"
     else
         echo "[INFO] machine-id is okay"
     fi