tests: ceph-disk: ignore E722 in flake8 test

tests: ceph-disk: ignore E722 in flake8 test

Very old, and very new, versions of flake8 treat E722 as an error:

flake8 runtests: commands[0] | flake8 --ignore=H105,H405,E127 ceph_disk tests
ceph_disk/main.py:1575:9: E722 do not use bare except'
ceph_disk/main.py:1582:9: E722 do not use bare except'
ceph_disk/main.py:3252:5: E722 do not use bare except'
ceph_disk/main.py:3288:21: E722 do not use bare except'
ceph_disk/main.py:3296:17: E722 do not use bare except'
ceph_disk/main.py:4358:5: E722 do not use bare except'
tests/test_main.py:26:1: E722 do not use bare except'
ERROR: InvocationError: '/opt/j/ws/mkck/src/ceph-disk/.tox/flake8/bin/flake8 --ignore=H105,H405,E127 ceph_disk tests'

Fixes: http://tracker.ceph.com/issues/22207
References: https://gitlab.com/pycqa/flake8/issues/361

Signed-off-by: Nathan Cutler <ncutler@suse.com>