Show failure in ssl-opts.sh when key export fails

1. When `ssl_server2` export key functionality fails,
don't exit the server, but reset it, to have the
server recover for next connection.
2. Add text filters for `export keys functionality` test in ssl-opt.sh
to check for additional output, to verify if the export suceeded.

This was discovered in the `ssl-opt.sh` script, where the server exited,
before the test tried to kill the server priocess, resulting in a
`kill: No such process` message.

Fixes #2662

Signed-off-by: Ron Eldor <Ron.Eldor@arm.com>

programs/ssl/ssl_server2.c

@@ -3718,7 +3718,7 @@ handshake:
         {
             mbedtls_printf( " failed\n  ! mbedtls_ssl_tls_prf returned -0x%x\n\n",
                             (unsigned int) -ret );
-            goto exit;
+            goto reset;
         }
 
         mbedtls_printf( "    EAP-TLS key material is:" );
@@ -3739,7 +3739,7 @@ handshake:
          {
              mbedtls_printf( " failed\n  ! mbedtls_ssl_tls_prf returned -0x%x\n\n",
                              (unsigned int) -ret );
-             goto exit;
+             goto reset;
          }
 
         mbedtls_printf( "    EAP-TLS IV is:" );

tests/ssl-opt.sh

@@ -9141,7 +9141,11 @@ run_test    "export keys functionality" \
             -s "exported ivlen is "  \
             -c "exported maclen is " \
             -c "exported keylen is " \
-            -c "exported ivlen is "
+            -c "exported ivlen is " \
+            -c "EAP-TLS key material is:"\
+            -s "EAP-TLS key material is:"\
+            -c "EAP-TLS IV is:" \
+            -s "EAP-TLS IV is:"
 
 # Test heap memory usage after handshake
 requires_config_enabled MBEDTLS_MEMORY_DEBUG