Test suites: print error on failed platform_setup

Return encountered errors instead of covering them
Fix return value on the broken snprintf implementation
diff --git a/tests/suites/helpers.function b/tests/suites/helpers.function
index c436fbb..f82694a 100644
--- a/tests/suites/helpers.function
+++ b/tests/suites/helpers.function
@@ -132,13 +132,11 @@
 /* Helper Functions */
 static int platform_setup()
 {
+    int ret = 0;
 #if defined(MBEDTLS_PLATFORM_C)
-    if( mbedtls_platform_setup( &platform_ctx ) != 0 )
-    {
-        return -1;
-    }
+    ret = mbedtls_platform_setup( &platform_ctx );
 #endif /* MBEDTLS_PLATFORM_C */
-    return 0;
+    return( ret );
 }
 
 static void platform_teardown()