Add a security scanner api config object for params

Change SecScanAPI to use a uri creation func instead of test context

Pass config provider through validator context

Remove app config dependency for validators

util/config/validators/validate_signer.py

@@ -1,6 +1,5 @@
 from StringIO import StringIO
 
-from _init import config_provider
 from util.config.validators import BaseValidator, ConfigValidationException
 from util.security.signing import SIGNING_ENGINES
 
@@ -11,6 +10,7 @@ class SignerValidator(BaseValidator):
   def validate(cls, validator_context):
     """ Validates the GPG public+private key pair used for signing converted ACIs. """
     config = validator_context.config
+    config_provider = validator_context.config_provider
 
     if config.get('SIGNING_ENGINE') is None:
       return