We never want to exit whilst holding these locks as it deadlocks all python
threads. Add signal blocking around the lock critical part so a signal
shouldn't cause such an exit.
(Bitbake rev: de552cf58fcbdea64b359a0fdcdf3673da3a780d)
Signed-off-by: Richard Purdie <richard.purdie@linuxfoundation.org>
(cherry picked from commit a097755c671e2b530dea6200a94b39fa9dca246c)
Signed-off-by: Steve Sakoman <steve@sakoman.com>