audio policy engine: fix improper error log in getDevicesForRoleAndStrategy

Add missing case for role DEVICE_ROLE_DISABLED
in getDevicesForRoleAndStrategy().
Although setting the role as DEVICE_ROLE_DISABLED is not
implemented we should not log an error when the getter is called.

Bug: 181269159
Bug: 184065221
Test: make, flash and boot.
Change-Id: I7283d1bcc13b2cbffdb5040e35b5804d2c2e66b4