RHEL 7 boxes problem with invalid user shells

[Tim Bielawa]

Reported externally by @tremble:

On RHEL7 I'm getting the following error caused by jsonstats modules:

Error: Shell /bin/nologin must exist
Error: /Stage[main]/Rhusers/Rhusers::User[jsonstatsd]/User[jsonstatsd]/ensure: change from absent to present failed: Shell /bin/nologin must exist

This is an easy two-part fix.

1. Internally, we need to update the jsonstats user account to point at a valid shell
2. In the jsonstats package we need to be sure the shell is also valid