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)

(cherry picked from c97c0f0a0c8617042698665ec98a39ad89938647)

Change-Id: I5b7401f91e5fb4ce604ff17209e7c1260dd57503
Bug-Url: https://bugzilla.redhat.com/990144
Signed-off-by: Sandro Bonazzola <sbonazzo@redhat.com>