Adapted `unit.modules.virtualenv` to use `salttesting.mock`
Adapted `unit.modules.alternatives_test` to use `salttesting.mock`
Adapted `unit.modules.win_status_test` to use `salttesting.mock`
Adapted `unit.modules.archive_test` to use `salttesting.mock`
Adapted `unit.modules.gem_test` to use `salttesting.mock`
Adapted `unit.modules.pip_test` to use `salttesting.mock`
Adapted `unit.modules.poptgres_test` to use `salttesting.mock`
Adapted `unit.modules.rvm_test` to use `salttesting.mock`
Adapted `unit.payload_test` to use `salttesting.mock`
Adapted `unit.pillar_test` to use `salttesting.mock`
Adapted `unit.utils.warnings_test` to use `salttesting.mock`
Adapted `unit.states.file_test` to use `salttesting.mock`
Adapted `unit.states.gem_test` to use `salttesting.mock`
Adapted `unit.states.pip_test` to use `salttesting.mock`
Adapted `unit.states.rvm_test` to use `salttesting.mock`
Adapted `integration.modules.cmdmod` to use `salttesting.mock`
Adapted `integration.modules.django` to use `salttesting.mock`
Merge pull request #6897 from s0undt3ch/features/salttesting-mock

Use salttesting.mock which allows for cleaner tests skip if mock is not available.