Fix some CI tests

[plotnick]

Fixes some (but not all) of #204. Requires a new docker image from Omicron#1384 to allow Nexus to even potentially run (missing dependencies), and updates the omicron.toml configuration so that Nexus can run ([deployment] changes).

[plotnick]

Adding a dbg!(&err) on a failing test (test_cmd_auth) yields:

[src/cmd_auth.rs:635] &err = reqwest::Error {
    kind: Request,
    url: Url {
        scheme: "http",
        cannot_be_a_base: false,
        username: "",
        password: None,
        host: Some(
            Domain(
                "localhost",
            ),
        ),
        port: Some(
            8888,
        ),
        path: "//session/me",
        query: None,
        fragment: None,
    },
    source: hyper::Error(
        Connect,
        ConnectError(
            "tcp connect error",
            Os {
                code: 111,
                kind: ConnectionRefused,
                message: "Connection refused",
            },
        ),
    ),
}

[plotnick]

docker logs nexus shows:

nexus: error while loading shared libraries: libxmlsec1-openssl.so.1: cannot open shared object file: No such file or directory

So the problem is that Nexus isn't starting because it doesn't have all of its dependencies installed. In particular, xmlsec1 is a new(ish) dependency, added with the recent SAML work.

[karencfv]

NICE! Thanks @plotnick for fixing the auth tests!