Swap the order of configparser imports

The configparser backport package has un-understood issues parsing
our files. But the intent of the code is to use whichever is the
package for the version of python in use. So, instead of trying to
install the python3 version first, which can also result in loading
the backport package, first try the python2 package, so that if
configparser itself is loaded, it will be because we're running python3.

Change-Id: I7ef497127822d0110804b04a674f24c195a07278