Fix some minor editorial errors

change sub-section title from "Service runas user"
to "Run services as non-root user".
include link to Object Storage authentication system.
remove redundatn '->' characters under Tip.

Change-Id: Ic124ce41b6bbc1a7bffaa189eef6d089e41ded39
Closes-Bug: 1342382
Merge "Fix some minor editorial errors"