Enable master SSH connection sharing speeding up test runs.
The OpenSSH-based master SSH connection sharing patch has been merged int
master from upstream.

Review URL: http://codereview.chromium.org/536016
diff --git a/global_config.ini b/global_config.ini
index 39e9d9b..6666a4e 100644
--- a/global_config.ini
+++ b/global_config.ini
@@ -83,7 +83,7 @@
 ssh_engine: raw_ssh
 # Set to True to take advantage of OpenSSH-based connection sharing. This would
 # have bigger performance impact when ssh_engine is 'raw_ssh'.
-enable_master_ssh: False
+enable_master_ssh: True
 # Autotest server operators *really should* set this to True, specially if
 # using ssh_engine 'paramiko'.
 require_atfork_module: False