Now that we have a rhel70-fips distro in Evergreen lets test on it to make sure PyMongo can always be configured to work in a FIPS env.

• Test on 4.0+, since SCRAM-SHA-256 is required for auth
• The GridFS test suite will need some changes to set disable_md5=True when we're testing in a FIPS env. This will likely require reading an environment variable.