This change adds a new policy setting, "show_instance_secrets", whose
behavior mirrors that of the existing "show_passwords" policy setting.
Whereas "show_passwords" has historically blocked all sensitive
information from the node's driver_info field, the new setting blocks
all sensitive information from the node's instance_info field, including
image_url.
The name of the old setting, "show_passwords", is not being changed at
this time because such a change is not backwards-compatible. Instead,
the documentation string for this setting has been changed to clarify
what it does. Note that the behavior has not actually changed.
Note that this change moves the policy.check("show_password") call from
the Pecan hook into the API's Nodes() class, where the
policy.check("show_instance_secrets") is also added. This makes the code
a little cleaner and more maintainable, especially if we want to add any
more checks like this in the future.
As a result of this cleanup, the ironic-specific
RequestContext.show_password property is removed.
Partial-bug: #1530972
Partial-bug: #1526752
Related-bug: #1613903
Change-Id: I48493c53971cdab3b9122897e51322e19ce2f600