devtool / recipetool: use common code for launching editor
Looking at Chris Larson's code for starting the user's editor for
"recipetool newappend" it was slightly better than what I wrote for
"devtool edit-recipe" in that it checks VISUAL as well as EDITOR and
defaults to vi if neither are set, so break this out to its own function
and call it from both places. The broken out version passes shell=True
however in case it's a more complicated command rather than just a name
of an executable.
Signed-off-by: Paul Eggleton <paul.eggleton@linux.intel.com> Signed-off-by: Richard Purdie <richard.purdie@linuxfoundation.org>
