CN: add introspect command to show global system config

[Nischal Sheth]

Along the lines of ShowBgpInstanceConfigReq and ShowBgpNeighborConfigReq,
we should add an introspect command to display the CN's view of the global
system configuration i.e. show various fields in the BgpGlobalSystemConfig
object pointed to by the BgpServer.

[OpenContrail Admin (ci-admin-f)]

Review in progress for https://review.opencontrail.org/40556
Submitter: Narendranath (<email address hidden>)

[OpenContrail Admin (ci-admin-f)]

Reviewed: https://review.opencontrail.org/40556
Committed: http://github.com/Juniper/contrail-controller/commit/e9a95c2e58881a2b73e87279f8c6bf236d7d5196
Submitter: Zuul v3 CI (<email address hidden>)
Branch: master

commit e9a95c2e58881a2b73e87279f8c6bf236d7d5196
Author: Naren Karjala <email address hidden>
Date: Mon Mar 12 11:55:12 2018 -0700

Add Inrospect command to show BGP's global system config

1. Added support for Introspect BGP global system config
2. Added unit test config file for validation of the
BGP global system config params
3. Added unit-test for validating the above introspect config

Note: The build and unit-test logs are available:
/build/nkarjala/SB/mainline/global-config-test.log

Taken care of the review comments:
a) removed the member string in ShowBgpGlobalSystemConfigReq

Change-Id: I40f688ec6b826261dde0f2c662b2962eae8df322
Closes-Bug: #1722395

[OpenContrail Admin (ci-admin-f)]

Review in progress for https://review.opencontrail.org/41024
Submitter: Narendranath (<email address hidden>)