Update alarms-history.md

[sangupta01]

Fixed typo in #3. It should be contrail-stats.

[pcarver]

Contrail/Tungsten Fabric does not accept GitHub pull requests. All changes should be submitted via the Gerrit code review tool. If you're not familiar with Gerrit, take a look at section 4 of https://github.com/tungstenfabric/docs/blob/master/Contributor/GettingStarted/getting-started-with-opencontrail-development.md for more info.

The key points are that you need to login to https://review.opencontrail.org with an Ubuntu One account in order to establish your SSH public key. You need to clone the repos from Gerrit rather than (or in addition to) GitHub (or manually add an additional remote to an existing repo rather than cloning if you prefer). And you need to install and use the "git review" extension to Git in order to push changes to Gerrit.