gnutls-cli-debug: fix early break for no version supported check

gnutls-cli-debug: fix early break for no version supported check

Currently gnutls-cli-debug code hardodes index of tests, after which it
will check if any known protocols (SSL 3.0/TLS1.[0123]) are supported by
the server. However this number is hardcoded and thus easy to break.
This is exactly what happened after adding %ALLOW_SMALL_RECORDS check.
Two tests were added in front of tests lists without updating this
index.

So let's make this check robust by adding another test which will return
fatal error if no known protocols are supported. While we are at it,
also simplify tests loop by removing internal loop completely and
controlling opening/closing a socket with a flag.

Signed-off-by: Dmitry Eremin-Solenikov <dbaryshkov@gmail.com>