nfscl: Add a check for VREG for delegations

Since delegations are only issued for regular files, check
v_type to see if the query is for a regular file. This is
a simple optimization for the non-VREG case.
While here, fix a couple of global variable declarations.

This patch should only affect the NFSv4.1/4.2 behaviour
when delegations are enabled, which is not the default.

(cherry picked from commit 4308d6e0fc09c807483f09b8fea7f5182d19fd01)