[Bug 1087697] man page inaccuracy about --sig-proxy and --tty

[Red Hat Bugzilla]

https://bugzilla.redhat.com/show_bug.cgi?id=1087697

--- Comment #3 from Lukas Doktor  ---
Thanks for a quick reply. I tried the docker-io-0.10.0-2.fc20.x86_64 which
says:
       --sig-proxy=true|false:
              When set to true, proxify all received signals  to  the  process
              (even in non-tty mode). The default is true.

I'd really like to change it to "only in non-tty" with possible warning that
--tty=true is incompatible with --sig-proxy.