rauc status warns that it couldn't determine all boot states but still reports boot_status = bad #1751
Description
Describe the bug
When running rauc status as a non-root user that cannot run fw_printenv rauc warns that it couldn't determine all boot states. This can be misleading when only looking at that boot status lines and perhaps missing the warnings as they are already scrolled out of view. It could also potentially be problematic in scripting usage as rauc still exits with exit_code = 0.
Background information
$ rauc --version
rauc 1.14
with uboot bootloader backend
To Reproduce
run rauc status
Expected behavior
Rauc not reporting bot status "bad" when it can't figure out the boot status. Maybe show "unknown" or "n/a"?
Logs
$ rauc status
rauc-Message: 12:53:44.867: Using central status file /data/rauc.status
rauc-Message: 12:53:44.868: Using system config file /etc/rauc/system.conf
Error opening lock file /run/fw_printenv.lock
rauc-Message: 12:53:44.875: Failed to get boot state of 'rootfs.1': uboot backend: fw_printenv failed with exit code: 1
Error opening lock file /run/fw_printenv.lock
rauc-Message: 12:53:44.880: Failed to get boot state of 'rootfs.0': uboot backend: fw_printenv failed with exit code: 1
Failed to determine boot states: Could not determine all boot states
Error opening lock file /run/fw_printenv.lock
Failed getting primary slot: uboot backend: fw_printenv failed with exit code: 1
=== System Info ===
[...] normal output continues
Additional context
The rauc service is not used here.