Reject TLS/SSL certificates which use MD2 or MD4.

TLS/SSL certificates which use MD5 are already being rejected (see
https://android-review.googlesource.com/#/c/44621/). This CL adds
similar rejection logic for MD2 and MD4 which are weaker than MD5.

Bug: 17177978
Change-Id: I3ae872dfc43b39ef000e027f9d4b6e5893ca32db
Merge "Reject TLS/SSL certificates which use MD2 or MD4."