Rename _ssh_sock() to fix code style issue.

Since _ssh_sock is imported out of the git_command module, the leading
underscore should be removed from the function name.
diff --git a/git_config.py b/git_config.py
index 45a2d25..a7c8210 100644
--- a/git_config.py
+++ b/git_config.py
@@ -23,7 +23,7 @@
 from urllib2 import urlopen, HTTPError
 from error import GitError, UploadError
 from trace import Trace
-from git_command import GitCommand, _ssh_sock
+from git_command import GitCommand, ssh_sock
 
 R_HEADS = 'refs/heads/'
 R_TAGS  = 'refs/tags/'
@@ -371,7 +371,7 @@
     return False
 
   command = ['ssh',
-             '-o','ControlPath %s' % _ssh_sock(),
+             '-o','ControlPath %s' % ssh_sock(),
              '-p',str(port),
              '-M',
              '-N',
@@ -399,7 +399,7 @@
       pass
   _ssh_cache.clear()
 
-  d = _ssh_sock(create=False)
+  d = ssh_sock(create=False)
   if d:
     try:
       os.rmdir(os.path.dirname(d))