SSLSocketTest: add error message test for fallback_scsv

The upgrade to OpenSSL 1.0.1j caused a regression for the error message
produced by inappropriate fallback protection mechanism. Add a test to
make sure this doesn't happen again.

Bug: 18018599
Change-Id: If8896d8f644095c13cbe44dd8ba7d4ef235385cf
1 file changed