Changed behavior of normalize to cause it to always override port and user
with values from ssh config.  This will require those who wish to override
ssh config values to do so in the host_string itself.  Before this, if the
port or user were set for one host then execute(..., hosts=[x,y,z]) was used,
the port and user would only be taken from the ssh config if these weren't
set for the current host in the master task.  The only options were to
save and clear these values before calling execute or to specify the port or
user in the host_string along with the hostname from ssh config.

This is very, very confusing and it only buys people a second method
of overriding what they probably didn't mean to override if they're
using use_ssh_config in the first place.