[chef] Passing on_error config to knife ssh

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We are using knife ssh to trigger simultaneous chef-client runs across 
multiple
instances present in AWS. However whenever the IP address of an EC2 instance
changes, the resulting chef search returns older IP addresses which 
effectively
lead to a warning indicating that it failed to connect to the instance.

WARNING: Failed to connect to  -- Errno::ETIMEDOUT: Connection timed out -
connect(2)

Ideally I'd like to set the on_error knife ssh config variable to :raise
instead of :skip so that knife ssh fails with a non-zero exit code. How do I 
go
about setting this config attribute? Is it possible to set this in knife.rb?