Add refusal of requests with forbidden parameters
Add refusal of requests with forbidden parameters

This patch provides the meat of the patch series by wrapping method
handlers in a function which examines parameters, and determines if
any of them are forbidden, whether specific values or in general.

Signed-off-by: Hrvoje Ribicic <be5828fca31f89218048bec4189e30a581aa65da@google.com>
Reviewed-by: Klaus Aehlig <4ce51de36d9068cd7db2eec1151e0f3f95419008@google.com>

andir/ganeti,andir/ganeti,ganeti/ganeti,mbakke/ganeti,leshchevds/ganeti,ganeti-github-testing/ganeti-test-1,yiannist/ganeti,ganeti-github-testing/ganeti-test-1,mbakke/ganeti,ganeti/ganeti,bitemyapp/ganeti,dimara/ganeti,apyrgio/ganeti,bitemyapp/ganeti,leshchevds/ganeti,dimara/ganeti,ganeti/ganeti,grnet/snf-ganeti,mbakke/ganeti,leshchevds/ganeti,grnet/snf-ganeti,andir/ganeti,yiannist/ganeti,yiannist/ganeti,onponomarev/ganeti,onponomarev/ganeti,apyrgio/ganeti