Fix detection of enterprise versions in 4.4+

[alcaeus]

MongoDB 4.4 changes the output of mongod --version, which breaks active version detection when an enterprise version is active:

$ m
  ο 4.2.12-ent 
    4.4.3-ent 
$ mongod --version
db version v4.2.12
git version: 5593fd8e33b60c75802edab304e23998fa0ce8a5
allocator: system
modules: enterprise 
build environment:
    distarch: x86_64
    target_arch: x86_64

$ m 4.4.3-ent
Activating 4.4.3-ent

$ mongod --version
db version v4.4.3
Build Info: {
    "version": "4.4.3",
    "gitVersion": "913d6b62acfbb344dde1b116f4161360acd8fd13",
    "modules": [
        "enterprise"
    ],
    "allocator": "system",
    "environment": {
        "distarch": "x86_64",
        "target_arch": "x86_64"
    }
}

$ m
    4.2.12-ent 
    4.4.3-ent 

I'm not sure the solution suggested here is free of unwanted side effects, but it's the best I could come up with. egrep works line by line, so we can't match on the JSON output directly. The updated regular expression matches on both 4.2 and 4.4:

$ /usr/local/m/versions/4.2.12-ent/bin/mongod --version | egrep "(modules:\s*)|\"enterprise\"?"
modules: enterprise 

$ /usr/local/m/versions/4.4.3-ent/bin/mongod --version | egrep "(modules:\s*)|\"enterprise\"?"
        "enterprise"

[stennie]

LGTM, thanks @alcaeus !

[alcaeus]

Thanks for the quick merge @stennie! ❤️