Fix URL checking on REST plugins

Fix URL checking on REST plugins

The URL parameter must always be provided on the REST client carrier plugin

The URL parameter must always be provided on the REST requestor consumer

The URL parameter is not required on the REST requestor producer

This patch fixes the implementation to always checks the URL for existence on
the REST Client plugin. The current checks on the REST Requestor are correct
for the REST requestor plugin consumer and producer classes, so the checks
are not required in the REST Requestor parameters.

Issue-ID: POLICY-2692
Change-Id: I4e1534202002cf4a03bd159ac97b2a4f5b1746ab
Signed-off-by: liamfallon <liam.fallon@est.tech>