admin: Add a check to reject negative argument for number of typed params

Since nparams can be technically negative, it is a good practice throughout
our code to check if nparams actually has a non-negative value. The same effect
would be achieved by converting our internal typed params serializer argument
to 'unsigned' type, but it definitely would not be the path of least resistance.
Signed-off-by: NErik Skultety <eskultet@redhat.com>

src/libvirt-admin.c

@@ -838,6 +838,7 @@ virAdmServerSetThreadPoolParameters(virAdmServerPtr srv,
 
     virCheckAdmServerReturn(srv, -1);
     virCheckNonNullArgGoto(params, error);
+    virCheckNonNegativeArgGoto(nparams, error);
 
     if (remoteAdminServerSetThreadPoolParameters(srv, params,
                                                  nparams, flags) < 0)