fedabipkgdiff: Remove busy loop when forking abipkgdiff

The function abipkgdiff() introduced a busy loop instead of using
subprocess.communicate() because it was randomly hanging back in the
python2 days.

This patch removes the busy loop altogether as I could not reproduce
the hanging anymore.

	* tools/fedabipkgdiff (abipkgdiff): Remove the busy looping and
	use subprocess.communicate() instead.

Signed-off-by: Dodji Seketeli <dodji@redhat.com>

tools/fedabipkgdiff

@@ -1182,30 +1182,8 @@ def abipkgdiff(cmp_half1, cmp_half2):
     proc = subprocess.Popen(' '.join(cmd), shell=True,
                             stdout=subprocess.PIPE, stderr=subprocess.PIPE,
                             universal_newlines=True)
-    # So we could have done: stdout, stderr = proc.communicate()
-    # But then the documentatin of proc.communicate says:
-    #
-    #    Note: The data read is buffered in memory, so do not use this
-    #    method if the data size is large or unlimited. "
-    #
-    # In practice, we are seeing random cases where this
-    # proc.communicate() function does *NOT* terminate and seems to be
-    # in a deadlock state.  So we are avoiding it altogether.  We are
-    # then busy looping, waiting for the spawn process to finish, and
-    # then we get its output.
-    #
 
-    sleeptime = 0.2
-    while True:
-        if proc.poll() != None:
-            break
-        time.sleep(sleeptime)
-        # cap the sleep time at 1.6s
-        if sleeptime < 2.0:
-            sleeptime = sleeptime * 2
-
-    stdout = ''.join(proc.stdout.readlines())
-    stderr = ''.join(proc.stderr.readlines())
+    stdout, stderr = proc.communicate()
 
     is_ok = proc.returncode == ABIDIFF_OK
     is_internal_error = proc.returncode & ABIDIFF_ERROR or proc.returncode & ABIDIFF_USAGE_ERROR