udevadm: Propagate return code from verb result

udevadm: Propagate return code from verb result

udevadm lock did not propagate the return code from the child process
because all positive values were treated as success.

v2:
Now 'udevadm test-builtin' ignores all positive return values from the
builtin commands. Otherwise, as the hwdb builtin returns an positive value
when a matching entry found, 'udevadm test-builtin hwdb' will fail.

v3:
Initialize partition table before calling 'sfdisk --delete'.

Co-authored-by: Yu Watanabe <watanabe.yu+github@gmail.com>