Refactor releng/prototypes/xci to releng-xci/xci in the code

Refactor releng/prototypes/xci to releng-xci/xci in the code

These changes are needed as part of migrating xci from releng repo to the releng-xci repo.
They cover:
- README updates
- Re-point configuration from releng/prototypes to releng-xci

The changes have been tested as follows:
- XCI_FLAVOR=aio
- OPENSTACK_OSA_VERSION=adfaa66d6108f87599e0595591b39cad2c8fb658
xci: aio has been installed

real    107m5.310s
user    11m50.180s
sys     4m11.152s
ubuntu@rack-IRA2-SymKloudBlade4:~/releng-xci/xci$

Change-Id: I8fd86c2442ee3a7c6996eedb6510dbc6eebd30b0
Signed-off-by: Dave Urschatz <dave.urschatz@cengn.ca>