ui/knotty.py: Fix signal handling of SIGWINCH in BBProgress

ui/knotty.py: Fix signal handling of SIGWINCH in BBProgress

Add the ability to pass default signal handler for SIGWINCH in BBProgress
because with multiple instace of BBProgress the original signal handler
set by TerminalFilter (sigwinch_handle) is lost.

This is a fix for stack trace due to multiple async calls of ProgressBar
_handle_resize (ioctl to terminal fd), see:

NOTE: Executing SetScene Tasks
Fatal Python error: Cannot recover from stack overflow.

Current thread 0x00007f70a4793700 (most recent call first):
  File
"/home/alimonb/repos/poky/bitbake/lib/progressbar/progressbar.py", line
183 in _handle_resize
  File "/home/alimonb/repos/poky/bitbake/lib/bb/ui/knotty.py", line 58
in _handle_resize
  File "/home/alimonb/repos/poky/bitbake/lib/bb/ui/knotty.py", line 60
in _handle_resize
...
  File "/home/alimonb/repos/poky/bitbake/lib/bb/ui/knotty.py", line 60
in _handle_resize
...
Aborted

Signed-off-by: Aníbal Limón <anibal.limon@linux.intel.com>
Signed-off-by: Richard Purdie <richard.purdie@linuxfoundation.org>