jstests/noPassthroughWithMongod/

• host_connection_string_validation.js
• ipv6_connection_string_validation.js
• replset_host_connection_validation.js

All check exitcode rather than the lexically scoped exitCode variable they use when running the shell. This makes debugging a little noisy (as you get a reference error, rather than being directly notified that the inner test failed)