lockd: fix a leak in nlmsvc_testlock asynchronous request handling

Without the patch, there is a leakage of nlmblock structure refcount
that holds a reference nlmfile structure, that holds a reference to
struct file, when async GETFL is used (-EINPROGRESS return from
file_ops->lock()), and also in some error cases.

Fix up a style nit while we're here.

Signed-off-by: Oleg Drokin <green@linuxhacker.ru>
Signed-off-by: J. Bruce Fields <bfields@citi.umich.edu>