Add coverity push script

[paul-elliott-arm]

Description

This is the script to allow us to push coverity builds from Jenkins (or anyone's machine come to that)

Functionality is documented within the script, but to test:

either:

export COVERITY_TOKEN=token
path/to/mbedtls/scripts/push_coverity_scan.py path/to/mbedtls -b origin/coverity_scan -e email@arm.com

or

path/to/mbedtls/scripts/push_coverity_scan.py path/to/mbedtls -t token -b origin/coverity_scan -e email@arm.com

The token can be found from the coverity web interface, and for the email address I would use your own email address for now (email address is unfortunately compulsary). Conversations are ongoing about which address to use for notifications in the future, the notification email will look like this:

 Your request for analysis of ARMmbed/mbedtls has been completed successfully.
    The results are available at <url>

    Build ID: 607763

    Analysis Summary:
       New defects found: 0
       Defects eliminated: 0

Should new defects be found, another email will be generated, but this will go to the whole team (this is specified within coverity itself)

WARNING - the mbedtls directory specified will be switched to the latest version of the branch specified, any outstanding differences will currently cause the script to fail (in my opinion better than forcing anything).

This constitutes stage 1 of getting coverity push back into CI, getting this script reviewed so that we can at least check its in the correct shape, then stage 2 will be adding the groovy and testing in the repo. I currently envisage this to be added shortly after the existing push from development to coverity_scan branches in the nightly runs.

[paul-elliott-arm]

One possible improvment (although not yet required) would be to parameterise the project so that we can easily use this on other projects, however I'm not sure how many coverity scan projects we are allowed to have!