object-storage: remove extraneous system calls

Remove a number of stat() system calls that were redundant, and remove
wayward open/close sequences, don't issue unlinks when we know the
temp file was successfully renamed, use rename() system call directly
to avoid stat() call ussed by swift's renamer(), use stat module
constants for supportability, and finally fix the .spec files so that
/etc/swift is not overwritten during installs.

Change-Id: Ie6b16596796c935286dd55f1788fd4c37a0e1f21
Signed-off-by: Peter Portante <peter.portante@redhat.com>