devtool: stop always moving workspace to end of BBLAYERS

devtool: stop always moving workspace to end of BBLAYERS

I noticed that using bitbake-layers add-layer followed by a devtool
command resulted in bitbake re-parsing all of the recipes, which is
annoying. Upon closer inspection I could see that devtool was moving the
workspace layer path to the end of BBLAYERS if it happened to be
somewhere in the middle - there's no need for it to be doing this. This
occurred because we were passing the current workspace path to remove
and the "new" path to add even if the path is not being changed, and I
think earlier versions of bb.utils.edit_bblayers_conf() didn't move the
existing entry under these circumstances as it clearly does now. Fix it
so we only pass the path to be removed if we're actually changing the
path.

(From OE-Core rev: 284426dbad91a3c52eaf7da5c58fe8a2c2dfb826)

Signed-off-by: Paul Eggleton <paul.eggleton@linux.intel.com>
Signed-off-by: Ross Burton <ross.burton@intel.com>
Signed-off-by: Richard Purdie <richard.purdie@linuxfoundation.org>