environs/jujutest: fix test
Fix TestBootstrapWithDefaultSeries.
It relied on the environment being unbootstrapped.
Gustavo thinks this test should really
be deleted, and replaced by a functional
test elsewhere, but I'd like to do both
at the same time when we do that.
R=jameinel, dimitern
CC=
https://codereview.appspot.com/7179043