Better pg_hba defaults and better password setup (IMVHO)

Default value for attribute ['postgresql']['pg_hba'] is an empty array
so it’s easier to override with Chef’s merge behavior.

Role’s password is set before the configurations are reloaded in order
to avoid problems if these configurations alter the authentication in
a significant way.

* cookbooks/postgresql/recipes/server.rb:
* cookbooks/postgresql/attributes/default.rb: