test_spec: Clarify RFC2889.MaxForwardingRate

test_spec: Clarify RFC2889.MaxForwardingRate

Changes based on review from VSPERF weekly call 2015-07-01.

* Change name from ForwardingRate to MaxForwardingRate
* Add section number to reference to RFC2889.

JIRA: VSPERF-33

Change-Id: Ic4ff9be5cf6a3d61fb5aa7c3216d3ff7c348677b
Signed-off-by: Billy O'Mahony<billy.o.mahony@intel.com>
Reviewed-by: Al Morton <acmorton@att.com>
Reviewed-by: Eugene Snider <Eugene.Snider@huawei.com>
Reviewed-by: Maryam Tahhan <maryam.tahhan@intel.com>
Reviewed-by: Gurpreet Singh <gurpreet.singh@spirent.com>
Reviewed-by: Tv Rao <tv.rao@freescale.com>