Use "checksums" args when calling "postgres.datadir_init"

[meaksh]

What does this PR do?

This PR fixes an issue inside postgres.datadir_init that is causing the accepted argument checksums is not being taken into account.

Therefore, without this PR, when you execute postgres.datadir_init or postgres_initdb.present state, the checksums argument is not used.

Previous Behavior

Given the following state:

pgsql-data-dir:
  postgres_initdb.present:
    - name: /var/lib/pgsql/data
    - auth: password
    - user: postgres
    - password: xxxxxx
    - encoding: UTF8
    - locale: C
    - runas: postgres
    - checksums: true

After applying it, the created DB is not created properly:

# su - postgres
postgres@postgres:~> psql
Password:
psql (10.10)
Type "help" for help.

postgres=# show data_checksums;
 data_checksums
----------------
 off                                                                                                                                                                                                 
(1 row)

postgres=#

New Behavior

Applying the same state produces a DB created successfully:

# su - postgres
postgres@postgres:~> psql
Password:
psql (10.10)
Type "help" for help.

postgres=# show data_checksums;
 data_checksums
----------------
 on                                                                                                                                                                                                 
(1 row)

postgres=#

Tests written?

[NOTICE] Bug fixes or features added to Salt require tests.
Please review the test documentation for details on how to implement tests into Salt's test suite.

Yes

Commits signed with GPG?

Yes

[dwoz]

@meaksh This needs to be re-opened against the master branch. We are no
longer accepting PRs to the 2019.2. If this fixes a bug in a 2019.2.x
release, please make note of it in your PR to master. Thanks!