Fix Nova-compatible Serial Console's Other deployer impact
Fix Nova-compatible Serial Console's Other deployer impact

This is a follow-up patch of 75290c72f7c3138bfdab151728718f771dfb9685
adds explanation about config option [console]terminal
and remove detail config file part.

Change-Id: I295ddd245e6bf4e7d132d3772f5b0465dec80227
Related-Bug: #1553083

bcornec/ironic-specs,NaohiroTamura/ironic-specs,openstack/ironic-specs