Support for 'package uninstall'

[kokosing]

As there is 'package install', but no support 'package uninstall' or 'update', So there is no way to update a package.

[cawallin]

'package uninstall' should be quite similar to 'package install'. It needs to uninstall a given RPM package on all of the nodes of the cluster.

A few notes:

• presto-admin is based on Fabric (http://docs.fabfile.org/en/1.10/), and most of the annotations are from Fabric.
• The @runs_once annotation requires some trickery to make the unit tests work correctly; check out other unit tests that use that annotation to see the way to get around it
• In addition to unit tests, we write product tests for presto-admin. These run on a docker cluster that the tests create locally, and can be run via make test-all (optionally, you can specify the suite -- aka tests.product.test_package_install -- to run only the relevant tests). They are located in tests/product.

[kokosing]

Fixed by 502de65