fix: Handle terraform crashes (#58)

When Terraform crashes the error code is 11 not 1.

Author: grahamhar

tftest.py

@@ -579,7 +579,7 @@ def execute_command(self, cmd, *cmd_args):
       raise TerraformTestError('Terraform executable not found: %s' % e)
     out, err = p.communicate()
     full_output = "".join(full_output_lines)
-    if retcode == 1:
+    if retcode in [1, 11]:
       message = 'Error running command {command}: {retcode} {out} {err}'.format(
           command=cmd, retcode=retcode, out=full_output, err=err)
       _LOGGER.critical(message)