nsm: Differentiate status contexts in verify job and bugfix

nsm: Differentiate status contexts in verify job and bugfix

The GitHub Pull Request Plugin publishes status messages to GitHub PR
for developers to see the results of verification. In previous job
configuration, status context was same for all jobs, overriding each
others status contexts and preventing to show statuses of different jobs.
This change uses different context based on what job does so the feedback
can be posted properly.

Example with same contexts: https://github.com/Nordix/Meridio/pull/1
Example with different contexts: https://github.com/Nordix/Meridio/pull/2

Auth ID was still wrong so that is fixed as well and a note is included
in jjb yaml to ensure it is not missed again.

Git SCM URL is also fixed in periodic job.

Change-Id: Iece387fec405b917ec1ae7b7704d4b85c79c45b4