Correct update ca certs command for Debian.
Test Plan:
Verify: Bootstrap and adding a Subcloud on Debian
Verify: Bootstrap and adding a Subcloud on Centos
Story: 2010119
Task: 45763
Signed-off-by: Li Zhu <li.zhu@windriver.com>
Change-Id: I4a9d2758ce012557fad4a19b49aa9b5bfe4f1680