Revert "devtool/standard.py: Not filtering devtool workspace for devtool finish"

This reverts commit 41d225f4a37d02e9f79bdbfb79caac8cd3d291ce.

Unfortunately this change broke 'devtool upgrade' functionality,
causing 'devtool finish' to write out an upgraded recipe that no
longer includes the original upstream source in SRC_URI.

Signed-off-by: Alexander Kanavin <alex.kanavin@gmail.com>
Signed-off-by: Richard Purdie <richard.purdie@linuxfoundation.org>