Fix use of TOOLS_TESTING_MONGOD with development server builds

[FGasper]

It’s helpful to be able to run tests locally using the same clusters that other provisioning tools use. configureClient(), however, only honors the hosts from the connection string, not the authentication.

Additionally, the logic to extract a MongoDB version from buildInfo’s versionArray did not account for the mismatch between that field and version in development builds. Also, certain tests that require an unauthenticated connection did not skip appropriately under authentication.

This changeset fixes both of those oversights so that it’s now possible to run the integrations tests thus:

TOOLS_TESTING_MONGOD='...' TOOLS_TESTING_INTEGRATION=1 go test -v ./...

… even when the connection string is authenticated and/or a development server.