In practice we found that there is a time during which kata-agent is
launched but the network of the pod is not prepared. In such case the
connection request from attestation-agent to KBS would fail because of
there is no network routine to the KBS.

This commit brings a retry mechanism for RCAR handshake. This will help
to resolve the problem.

Signed-off-by: Xynnn007 <xynnn@linux.alibaba.com>

Make the provider name recognization case insensitive.

Signed-off-by: Xynnn007 <xynnn@linux.alibaba.com>

Signed-off-by: Xynnn007 <xynnn@linux.alibaba.com>

Signed-off-by: Xynnn007 <xynnn@linux.alibaba.com>