Currently init-runonce script changes directory to the
script's base directory (/usr/...) before doing anything else.
This unnecessarily _forces_ a non-root user to use sudo for
running this script thereby raising privileges for code which
doesn't want it. Also downloading temporary stuff in places like
/usr... seems not a good choice.

Hence deleting the said code part and letting the deployer work
comfortably from any directory.

Made documentation changes accordingly.

Change-Id: Ib3c7ed97aa5f53c115b6337aaf572b5fdc7a71f3
Closes-Bug: #1732963