flake8: Ignore bare except violations

flake8: Ignore bare except violations

Newer versions of flake8 (3.5.0, mccabe: 0.6.1, pycodestyle: 2.3.1,
pyflakes: 1.6.0) add an error code for 'bare exception'.  The OvS
codebase does use bare exceptions in places, especially when the
specific exception isn't important (ie: the program will be
terminating, so the specific exception isn't important).

Without this change, the following error messages appear:
   utilities/checkpatch.py:476:5: E722 do not use bare except'
   utilities/checkpatch.py:514:5: E722 do not use bare except'
   utilities/ovs-dev.py:189:5: E722 do not use bare except'
   utilities/ovs-dev.py:192:9: E722 do not use bare except'
   utilities/ovs-dev.py:197:5: E722 do not use bare except'
   utilities/bugtool/ovs-bugtool.in:360:13: E722 do not use bare except'
   utilities/bugtool/ovs-bugtool.in:434:5: E722 do not use bare except'
   utilities/bugtool/ovs-bugtool.in:470:13: E722 do not use bare except'
   utilities/bugtool/ovs-bugtool.in:609:9: E722 do not use bare except'
   utilities/bugtool/ovs-bugtool.in:679:5: E722 do not use bare except'
   utilities/bugtool/ovs-bugtool.in:712:13: E722 do not use bare except'
   utilities/bugtool/ovs-bugtool.in:744:9: E722 do not use bare except'
   utilities/bugtool/ovs-bugtool.in:751:9: E722 do not use bare except'
   utilities/bugtool/ovs-bugtool.in:825:5: E722 do not use bare except'
   utilities/bugtool/ovs-bugtool.in:1006:13: E722 do not use bare except'
   utilities/bugtool/ovs-bugtool.in:1041:13: E722 do not use bare except'
   utilities/bugtool/ovs-bugtool.in:1079:5: E722 do not use bare except'
   utilities/bugtool/ovs-bugtool.in:1202:5: E722 do not use bare except'
   utilities/bugtool/ovs-bugtool.in:1247:9: E722 do not use bare except'
   utilities/bugtool/ovs-bugtool.in:1257:13: E722 do not use bare except'
   utilities/bugtool/ovs-bugtool.in:1328:9: E722 do not use bare except'
   tests/test-daemon.py:60:5: E722 do not use bare except'
   tests/test-l7.py:23:1: E722 do not use bare except'
   tests/test-unixctl.py:96:5: E722 do not use bare except'
   xenserver/usr_share_openvswitch_scripts_ovs-xapi-sync:404:5: E722 do not use bare except'
   python/ovs/fcntl_win.py:39:9: E722 do not use bare except'
   python/ovs/poller.py:38:1: E722 do not use bare except'
   python/ovs/socket_util.py:151:13: E722 do not use bare except'
   python/ovs/stream.py:169:17: E722 do not use bare except'
   python/ovs/stream.py:578:17: E722 do not use bare except'
   python/ovs/timeval.py:51:1: E722 do not use bare except'
   python/ovstest/util.py:52:5: E722 do not use bare except'
   vtep/ovs-vtep:767:5: E722 do not use bare except'

Signed-off-by: Aaron Conole <aconole@redhat.com>
Signed-off-by: Ben Pfaff <blp@ovn.org>