CP-7327 nice and ionice config options for sparse_dd.conf

Signed-off-by: Thomas Sanders <thomas.sanders@citrix.com>
(cherry picked from commit 1614b17016d2122ef0661c312648559ea67ba874)
Merge pull request #5 from thomassa/br0.6.4-with-nice

CP-7327 nice and ionice config options for sparse_dd.conf