Separate refresh test suites

[farshidtz]

The refresh test requires a very different setup and teardown process because it involves upgrading from an older to the current (under test) snap. This adds complication because when refresh tests run in the middle of other tests, the current snap is removed in setup and installed again in teardown.

Testing the refresh test alone will result in an unwanted workflow:

1. install current (global setup)
2. remove current (setup)
3. install old snap (setup)
4. refresh to current
5. remove current (cleanup)
6. install current (cleanup)
7. remove current (global teardown)

go test -p 1 ./test/suites/edgexfoundry -run=TestCommon/refresh -v