upload: nfs: set correct umask while renaming

set the correct umask while renaming the temporary
file to destination file. Avoid to have incorrect
access bits on systems with not standard umask
(like 077)

Change-Id: I5b7401f91e5fb4ce604ff17209e7c1260dd57503
Bug-Url: https://bugzilla.redhat.com/988146
Signed-off-by: Sandro Bonazzola <sbonazzo@redhat.com>