net: add test for TLS_FALLBACK_SCSV

BUG=310768

Review URL: https://codereview.chromium.org/109563002

git-svn-id: svn://svn.chromium.org/chrome/trunk/src@240163 0039d316-1c4b-4281-b951-d872f2087c98
SVN changes up to revision 240163