Rename isolated creds to dynamic creds

Renaming the isolated_creds module to dynamic_creds module, and rename
the IsolatedCreds class to DynamicCredentialProvider in preparation
to migration to tempest-lib.

Partially implements bp tempest-library

Change-Id: I78a4884e980ef7d0103639cb3792a54c69fb7761
diff --git a/tempest/cmd/verify_tempest_config.py b/tempest/cmd/verify_tempest_config.py
index 4fcdf8b..2811070 100755
--- a/tempest/cmd/verify_tempest_config.py
+++ b/tempest/cmd/verify_tempest_config.py
@@ -348,7 +348,7 @@
         CONF_PARSER = moves.configparser.SafeConfigParser()
         CONF_PARSER.optionxform = str
         CONF_PARSER.readfp(conf_file)
-    icreds = credentials.get_isolated_credentials('verify_tempest_config')
+    icreds = credentials.get_credentials_provider('verify_tempest_config')
     try:
         os = clients.Manager(icreds.get_primary_creds())
         services = check_service_availability(os, update)
@@ -370,7 +370,7 @@
             CONF_PARSER.write(outfile)
         outfile.close()
     finally:
-        icreds.clear_isolated_creds()
+        icreds.clear_creds()
 
 
 if __name__ == "__main__":