devtool: add: use correct bbappend file name with -V option
We weren't adding the version into the bbappend file name when -V was
specified which meant that building or resetting failed.
Also adjust one of the tests so that we're testing devtool add both with
and without this option.
Fixes [YOCTO #7647].
(From OE-Core master rev:
bdbeff0cd342e31053d7203d78fc5dda611052b1)
Signed-off-by: Paul Eggleton <paul.eggleton@linux.intel.com>
Signed-off-by: Richard Purdie <richard.purdie@linuxfoundation.org>
