NFS: use SUNRPC cache creation and destruction helper for DNS cache
NFS: use SUNRPC cache creation and destruction helper for DNS cache

This cache was the first containerized and doesn't use net-aware cache
creation and destruction helpers.
This is a cleanup patch which just makes code looks clearer and reduce amount
of lines of code.

Signed-off-by: Stanislav Kinsbursky <43b28e187c4fe6e53d7ab0bb71957481e322f182@parallels.com>
Signed-off-by: J. Bruce Fields <51738506c1b2ccb0761f23bdc612c93babf738ea@redhat.com>

TeamVee-Kanas/android_kernel_samsung_kanas,TeamVee-Kanas/android_kernel_samsung_kanas,KristFoundation/Programs,KristFoundation/Programs,KristFoundation/Programs,TeamVee-Kanas/android_kernel_samsung_kanas,TeamVee-Kanas/android_kernel_samsung_kanas,TeamVee-Kanas/android_kernel_samsung_kanas,KristFoundation/Programs,KristFoundation/Programs,KristFoundation/Programs