Fix wrong type in a docstring of the RAPI subsystem

Signed-off-by: Michele Tartara <mtartara@google.com>
Reviewed-by: Michael Hanselmann <hansmi@google.com>

lib/rapi/baserlib.py

@@ -298,7 +298,7 @@ class ResourceBase(object):
     return val
 
   def _checkStringVariable(self, name, default=None):
-    """Return the parsed value of an int argument.
+    """Return the parsed value of a string argument.
 
     """
     val = self.queryargs.get(name, default)