[ACS44] Fix for CLOUDSTACK-5501 and CLOUDSTACK-6607

[Sheng Yang]

Hi Daan,

Please cherry pick following commits in 4.4-forward branch for ACS 4.4's
fix.

commit a3e9d0ff12deb36fa304795a089345869cc29a08
Author: Sheng Yang <sheng.y...@citrix.com>
Date:   Mon May 12 18:26:53 2014 -0700

    CLOUDSTACK-5501: Allow one vpn customer gateway with multiple
connections

    This restriction was purposely avoid confusion of VPN setup, but later
found too
    strictly and cause troubles for deployment. Removed after testing one
customer
    gateway with multiple connections.

commit 4adee0a55e36045f2fd76b35b1cc7de14cb3493a
Author: Sheng Yang <sheng.y...@citrix.com>
Date:   Mon May 12 18:25:18 2014 -0700

    CLOUDSTACK-6607: Correct the result of VpcNetworkUsage

    Blank or not shouldn't be used to indicate command is failure or not.

Thanks!

--Sheng