Refactor tests/unit/states/test_sysctl.py
Refactor tests/unit/states/test_sysctl.py

The old test combined several different independent commands into a
single obese test case, with overlapping local variables.

Break it into small individual test cases.  Also, fix some of the mocks,
which only triggered correct behavior by coincidence.

saltstack/salt,saltstack/salt,saltstack/salt,saltstack/salt,saltstack/salt