Dovetail needs credentials file openrc as an input

Dovetail needs credentials file openrc as an input

1. The Dovetail tool itself needs openrc file as the input rather than
   INSTALLER_TYPE and INSTALLER_IP.
   See JIRA: DOVETAIL-369  and  JIRA: DOVETAIL-371
2. Now Dovetail CI jobs just give INSTALLER_TYPE and INSTALLER_IP
   to Dovetail tool.
3. So Dovetail CI jobs need to fetch the openrc file before
   and run Dovetail tool with the openrc file.

JIRA: DOVETAIL-372

Change-Id: I3a6293da621ae0a2f5d72a297d3d912fd60e05d8
Signed-off-by: xudan <xudan16@huawei.com>