Add vault credential to factory and provision_job_options.

[lfu]

• Add ansible_vault_credential into factory.
• Add vault credential to service's provision_job_options.

Blocks ManageIQ/manageiq-providers-ansible_tower#70.

@miq-bot assign @gmcculloug
@miq-bot add_label enhancement, gaprindashvili/yes, services

Part of https://bugzilla.redhat.com/show_bug.cgi?id=1526048 required to get to Embedded Ansible 3.2.x
Part of https://bugzilla.redhat.com/show_bug.cgi?id=1561116 required to get to Embedded Ansible 3.2.x

[miq-bot]

Checked commits lfu/manageiq@fcbbbb7~...84ee34e with ruby 2.3.3, rubocop 0.52.1, haml-lint 0.20.0, and yamllint 1.10.0
3 files checked, 0 offenses detected
Everything looks fine. 👍

[simaishi]

Gaprindashvili backport details:

$ git log -1
commit 1d081728431111d2e6d32290a0ffc5ab9f427a3e
Author: Greg McCullough <gmccullo@redhat.com>
Date:   Tue Mar 27 10:22:02 2018 -0400

    Merge pull request #17207 from lfu/ansible_vault_credential_3
    
    Add vault credential to factory and provision_job_options.
    (cherry picked from commit 1d647baa7207499b046aeda30447fab51b78798f)
    
    https://bugzilla.redhat.com/show_bug.cgi?id=1561146