Modify some spelling mistakes

There are some comment errors, it's modify 'Captial' to 'Capital' in
keystone file, and modify 'possition' to 'position' in openrc file, and
modify 'comming' to 'coming' in stack file, and
modify 'prefered' to 'preferred' in stackrc file.

Change-Id: I0fdd539cbfff842a4ba7fca9100b881443300f9a
4 files changed