calvincontrol: fix issue when data is not iterable
calvincontrol: fix issue when data is not iterable

In some cases the data coming in is not iterable,
but treated as one and fails with exception.

Signed-off-by: Robert Marklund <76bc9a6937e271e59d3e56f546e9e54d2b682cd6@ericsson.com>

EricssonResearch/calvin-base,EricssonResearch/calvin-base,EricssonResearch/calvin-base,EricssonResearch/calvin-base