Always enable ecdh_auto.
This is a really dumb API wart. Now that we have a limited set of curves that are all reasonable, the automatic logic should just always kick in. This makes set_ecdh_auto a no-op and, instead of making it the first choice, uses it as the fallback behavior should none of the older curve selection APIs be used. Currently, by default, server sockets can only use the plain RSA key exchange. BUG=481139 (cherry picked from commit dd978784) Change-Id: I2ef653236c55df0d990c01cfdcaedbd757062e46