Partial fix for LP-1351089
LP-1351089 :: Isolate tests from users BASH_ENV
Add comments per suggestion from @axw
Revert "Merge pull request #416 from axw/mongo-journalenabled"

This reverts commit 62e172632c3e9d8496805ed5223f9f4acc28986a, reversing
changes made to 8275fa461e1644ac073db177c5e456db24991a0c.
Merge pull request #454 from johnweldon/lp-1351089-isolate

LP-1351089 :: Isolate tests from users BASH_ENV

By suppressing bash from loading the BASH_ENV files
Merge pull request #450 from johnweldon/lp-1351089

Partial fix for LP-1351089

If the environment has `set -o noclobber` then `cat > $TMPFILE` will fail if $TMPFILE exists.

The test referenced in [lp-1351089](https://bugs.launchpad.net/juju-core/+bug/1351089) should still be isolated better from the environment, but this seems like a good change to make anyway.
Merge pull request #472 from mjs/fix-mongo-craziness

Revert "Merge pull request #416 from axw/mongo-journalenabled"

This reverts commit 62e172632c3e9d8496805ed5223f9f4acc28986a, reversing
changes made to 8275fa461e1644ac073db177c5e456db24991a0c.

The commit being reverted appears to cause mongo to consume large amounts of resources and get stuck when "juju ensure-availability" is run, effectively trashing the environment.