xci: Updates to releng/bifrost to make it work on Jenkins

xci: Updates to releng/bifrost to make it work on Jenkins

- get rid of BAREMETAL_DATA_FILE and use BIFROST_INVENTORY_SOURCE
so it works both for master and ocata for osa-bifrost.
- set BIFROST_INVENTORY_SOURCE file according to branch bifrost is
executed from for osa-bifrost.
- explicitly set what the SSH public key file is as ansible copies
the wrong public key to nodes if bifrost is executed on Jenkins
using sudo.
- set branches if they are not set so the scripts can be used manually
as well.
- rename jumphost to xcimaster so people do not mix it with actual
jumphost located in Pharos PODs.

Change-Id: Iff7631fa99816ad75316b62c5ac20714f67cd86a
Signed-off-by: Fatih Degirmenci <fatih.degirmenci@ericsson.com>