check_vxlan_support works incorrect on RHEL6.5

[JunJie Nan]

RHEL6.5 has back ported vxlan support feature into its kernel 2.6 but check_vxlan_support still give NOT result.

[OpenStack Infra (hudson-openstack)]

Fix proposed to branch: master
Review: https://review.openstack.org/65902

[OpenStack Infra (hudson-openstack)]

Reviewed: https://review.openstack.org/65902
Committed: https://git.openstack.org/cgit/openstack/neutron/commit/?id=d583d55c6a4e6c01c49411b7e5b519031bce0699
Submitter: Jenkins
Branch: master

commit d583d55c6a4e6c01c49411b7e5b519031bce0699
Author: JUN JIE NAN <email address hidden>
Date: Fri Jan 10 15:01:13 2014 +0800

    Check vxlan enablement via modinfo

    On some linux distribution, for RHEL 6.5 as an example, vxlan is
    enabled but the kernel version is still 2.6. And some linux kernel
    version is higher than 3.8 or even 3.11, its vxlan mod may be
    disabled. Under both situation, vxlan enablement checking via linux
    kernel version may not be correct.

    In this patch, we check vxlan enablement via modinfo: if vxlan module
    exists and functional test pass, vxlan is enabled.

    Closes-Bug: #1267682

    Change-Id: Id52c04b4739d2d11fe52d4b1631cb4f39e6b577f