tests: py: disable main_signon check for printenv cmd

if CONFIG_VERSION_VARIABLE is set, the U-Boot environment
contains a "vers" variable with the current U-Boot version
string. If now "printenv" is called, test/py fails as it
detects the main_sign string, which is in this case correct.

So check only the main_sign as an error, if CONFIG_VERSION_VARIABLE
is not set.

Signed-off-by: Heiko Schocher <hs@denx.de>
diff --git a/test/py/tests/test_env.py b/test/py/tests/test_env.py
index c41aa5a..22a22d1 100644
--- a/test/py/tests/test_env.py
+++ b/test/py/tests/test_env.py
@@ -39,7 +39,11 @@
             Nothing.
         """
 
-        response = self.u_boot_console.run_command('printenv')
+        if self.u_boot_console.config.buildconfig['config_version_variable'] == 'y':
+            with self.u_boot_console.disable_check('main_signon'):
+                response = self.u_boot_console.run_command('printenv')
+        else:
+            response = self.u_boot_console.run_command('printenv')
         self.env = {}
         for l in response.splitlines():
             if not '=' in l: