Restore backward compat for int/float in extra_specs

In icehouse, we were able to store ints, floats in
extra_specs, with I195bd5d45a896e9b26dd81dab1e49c9f939b4805 we
forced the value(s) to be just strings. Let's loosen up
this restriction and still enforce a length check.

Closes-Bug: #1358818
Change-Id: I7687d0214e44d4af1b595c6c6c7ce685d4083556
Merge "Restore backward compat for int/float in extra_specs"