cve-update-db-native: pycodestyle fixes

cve-update-db-native: pycodestyle fixes

Fixes following pycodestyle complaints:

  cve-update-db-native.bb:80:39: E712 comparison to True should be 'if cond is True:' or 'if cond:'
  cve-update-db-native.bb:128:20: E401 multiple imports on one line
  cve-update-db-native.bb:130:18: E401 multiple imports on one line
  cve-update-db-native.bb:171:21: E741 ambiguous variable name 'l'
  cve-update-db-native.bb:335:26: E225 missing whitespace around operator
  cve-update-db-native.bb:344:12: E713 test for membership should be 'not in'
  cve-update-db-native.bb:347:12: E713 test for membership should be 'not in'

Also leaves out a redundant 'gzip' import in update_db_file().

Signed-off-by: Niko Mauno <niko.mauno@vaisala.com>
Signed-off-by: Mathieu Dubois-Briand <mathieu.dubois-briand@bootlin.com>