generated_samples and generated_tests directories shouldn't install into site-packages root

Recently updated components of the Azure SDK for Python such as `azure-mgmt-compute` started to install two new directories into the `site-packages` directory which is shared across all Python packages on the system.

These two directories are called `generated_samples` and `generated_tests`. It's not clear to me whether these directories are necessary for the package to work and should be installed by the package manager.

It looks like at least the `generated_tests` directory may be helpful for running the testsuite of the package. In any case, the two directories should be installed into a directory inside the `azure` directory tree and not into the `site-packages` directory which is shared with other non-Azure Python packages.