Travis and test fixes:

- Build server build with latest C/C: Instead of copying the C/C directory
  into server, we now fetch the actual commit or PR into server repository
- Fix travis environment variables (Windows)
- Skip character set tests if the server doesn't support charset/collation
- Don't use CREATE OR REPLACE SQL syntax to make MySQL happy
- Disable TLS connection test for MaxScale
- Don't set TEST environment variables if they are empty

unittest/libmariadb/connection.c

@@ -2339,6 +2339,8 @@ static int test_conc748(MYSQL *my __attribute__((unused)))
   int i;
   const char *ciphers[3]= {"TLS_AES_128_GCM_SHA256", "TLS_AES_256_GCM_SHA384", "TLS_CHACHA20_POLY1305_SHA256"};
 
+  SKIP_MAXSCALE;
+
   for (i=0; i < 3; i++)
   {
     const char *tls_version;