Setting empty password causes exception...

[notapatch]

Setting an empty password for a pg_user causes an exception.

Bug

For pg_user.rb, the role_sql variable in Line 17 gets << a nil when there is no password and it throws an exception as it cannot implicitly convert nil into a string. My fix is to else an empty string.

Usage case

My usage case for no password. I configure a development systems and I want to create pg_user with the same name as a login. This gives my login user pg permissions, mainly CREATEDB, which is very useful to a rails developer.

Reproducing Error

Reproduce this in test-kitchen by converging with the following yml added.

 attributes:
      postgresql:
        users:
          - username: richard
            superuser: false
            createdb: true
            login: true

[phlipper]

@RichardWigley thank you very much for the detailed PR and fix! I have rebased this on top of the latest master and merged it in as #95

[notapatch]

And thank you for merging. :-)