Fix issue 1382: chown .sconsign.dblite back to original user/group when done, when running as root.  If it didn't exist, chown to user who executed sudo if known.  Hard to test automatically because test needs to run as root.
Fix issue 1382: chown .sconsign.dblite back to original user/group when done, when running as root.  If it didn't exist, chown to user who executed sudo if known.  Hard to test automatically because test needs to run as root.

andrewyoung1991/scons,andrewyoung1991/scons,timj/scons,timj/scons,andrewyoung1991/scons,timj/scons,andrewyoung1991/scons,timj/scons,andrewyoung1991/scons,timj/scons,andrewyoung1991/scons,timj/scons,timj/scons,timj/scons,timj/scons,andrewyoung1991/scons,andrewyoung1991/scons,andrewyoung1991/scons