Fix error when early data empty

This PR fixes an error when early data was empty
which caused testssl.sh to exit instead of marking
that there was no file returned.

Also it changes HEAD to GET as the latter is probably
more often supported.

There needs to be a unit test for 0-RTT / early data!

Author: drwetter

testssl.sh

@@ -7176,12 +7176,11 @@ sub_early_data() {
      else
           return 5
      fi
-
-     safe_echo "HEAD / HTTP/1.1\r\nHost: $NODE\r\nConnection: close\r\nEarly-Data: 1\r\n\r\n" > $early_data
+     safe_echo "GET / HTTP/1.1\r\nHost: $NODE\r\nEarly-Data: 1\r\nConnection: close\r\n\r\n" > $early_data
      $openssl_bin s_client $(s_client_options "$STARTTLS $BUGS -tls1_3 -connect $NODEIP:$PORT $PROXY $SNI") -sess_out $sess_data -ign_eof \
             < $early_data >/dev/null 2>$ERRFILE
      if [[ ! -s "$sess_data" ]]; then
-          exit 7
+          return 7
      fi
 
      $openssl_bin s_client $(s_client_options "$STARTTLS $BUGS -tls1_3 -connect $NODEIP:$PORT $PROXY $SNI") -sess_in $sess_data \
@@ -10804,7 +10803,7 @@ run_server_defaults() {
                6) prln_warning "Client Auth: early data check not supported"
                   fileout "$jsonID" "WARN" "check couldn't be performed because of client authentication"
                   ;;
-               7) prln_warning "check failed (no session data"
+               7) prln_warning "check failed (no session data received)"
                   fileout "$jsonID" "WARN" "check failed (no session data)"
                   ((ret++))
                ;;