TOOL-22328 Fix auto-updates for generic kernel on 5.15

PR URL: https://www.github.com/delphix/linux-pkg/pull/298

Author: Prakash Surya

default-package-config.sh

@@ -247,7 +247,7 @@ function kernel_update_upstream() {
 	local tag_prefix_flavour
 	case "${platform}" in
 	generic)
-		if [[ "$UBUNTU_DISTRIBUTION" == bionic ]]; then
+		if [[ "$UBUNTU_DISTRIBUTION" == focal ]]; then
 			tag_prefix_flavour="Ubuntu-hwe"
 		else
 			tag_prefix_flavour="Ubuntu"