Change tls client auth related options
Change tls client auth related options

This change is a feedback from a chrome network member.
See also, https://chromiumcodereview.appspot.com/10541168/

BUG=none
TEST=none

Review URL: https://codereview.appspot.com/6344112
GoogleChromeLabs/pywebsocket3,googlearchive/pywebsocket,google/pywebsocket,googlearchive/pywebsocket,google/pywebsocket,google/pywebsocket,googlearchive/pywebsocket,GoogleChromeLabs/pywebsocket3,GoogleChromeLabs/pywebsocket3