apibuild: Split imports on separate lines

PEP8 recommends imports to be on separate lines. [1]

1: https://www.python.org/dev/peps/pep-0008/#importsReviewed-by: NDaniel P. Berrangé <berrange@redhat.com>
Signed-off-by: NRadostin Stoyanov <rstoyanov1@gmail.com>

docs/apibuild.py

@@ -10,7 +10,8 @@
 
 from __future__ import print_function
 
-import os, sys
+import os
+import sys
 import glob
 import re