query the pip path for test test_issue_2087_missing_pip

[Ch3LL]

What does this PR do?

The following tests are failing on macosx python3:

integration.modules.test_pip.PipModuleTest.test_issue_2087_missing_pip                                                                                                              
integration.states.test_pip.PipStateTest.test_issue_2087_missing_pip

This is because when the virtualenv is created its created with python2 because the default python is 2 on the macosx hosts. My understanding of the virtualenv.create module is that it will use the default python version installed unless python=python3 is passed to the command. I could be wrong about this code analysis as I am not certain if its suppose to grab the version of python that salt is running.

This PR changes the test to query what the site-packages path is for the pip package before we try to remove it, instead of assuming the path is the same version of python as the test runner.

[twangboy]

@Ch3LL Actually I think the version of is bundled within virtualenv itself and does not rely on the System python. At least that's what I think @terminalmage and I worked out.