add 'check-cache' and 'update-cache' commands [1/2] (#5591)

ERRATUM: dcfbdbcdb8 was for #5458.

The cache is used for Jenkins and JClouds "binaries". Tests will follow.
* add tests for Jenkins and JClouds binaries' cache (#5591)
* fix long options capabilities
* refactoring (cache.py, test.PATHS, inherit test.TestJenkinsBase)