qa/878: try to avoid race after pmda install
qa/878: try to avoid race after pmda install

On vm01 this test consistently failed with no data found for first
pminfo ... adding a short sleep seems to have fixed it.

adfernandes/pcp,adfernandes/pcp,adfernandes/pcp,adfernandes/pcp,adfernandes/pcp,adfernandes/pcp,adfernandes/pcp,adfernandes/pcp