Stabilize repo communication with subprocesses.

Make repo use the standard way in python to work with pipes.
Communication via pipes to sub processes is done by calling
communicate(). This will make repo not hang every now and
then.

Change-Id: Ibe2c4ecbdbcbe72f0b725ca50d54088e5646fc5d

git_command.py

@@ -221,26 +221,10 @@ class GitCommand(object):
     self.stdin = p.stdin
 
   def Wait(self):
-    p = self.process
-
-    if p.stdin:
-      p.stdin.close()
-      self.stdin = None
-
-    if p.stdout:
-      self.stdout = p.stdout.read()
-      p.stdout.close()
-    else:
-      p.stdout = None
-
-    if p.stderr:
-      self.stderr = p.stderr.read()
-      p.stderr.close()
-    else:
-      p.stderr = None
-
     try:
-      rc = p.wait()
+      p = self.process
+      (self.stdout, self.stderr) = p.communicate()
+      rc = p.returncode
     finally:
       _remove_ssh_client(p)
     return rc