[FEATURE] three minor fixes to consider

[noelmcloughlin]

Is your feature request related to a problem?

Describe the solution you'd like

General issue

• The mongod.sh file contains superfluous {} line

  
  bobby@work kubernetes % cat /etc/default/mongod.sh 
  ########################################################################
  # File managed by Salt at <salt://mongodb/files/default/environ.sh.jinja>.
  # Your changes may be overwritten.
  ########################################################################

export PATH=${PATH}:/usr/local/mongodb/mongod-4.2.6 {}

**On MacOS-**

- The formula should manage `mongod.sh` in  `/etc/defaults/` not `/etc/default/`

      ID: mongodb-config-install-mongod-environ_file
Function: file.managed
    Name: /etc/default/mongod.sh
  Result: True
 Comment: File /etc/default/mongod.sh is in the correct state
 Started: 20:43:29.766874
Duration: 22.894 ms

- There should be symlinks from `/usr/local/mongo-xxxx/bin/cmd` to `/usr/local/bin/cmd`

bobby@work % ls /usr/local/mongodb/mongod-4.2.6/bin bsondump mongo mongodump mongofiles mongoreplay mongos mongotop install_compass mongod mongoexport mongoimport mongorestore mongostat

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