Let the Autopilot matrix script fail when gh fails

Use bash and pipefail for that. Also remove the usage for grep by
directly passing the filter value into the jq query.

Signed-off-by: Tom Wieczorek <twieczorek@mirantis.com>

hack/tools/gen-matrix.sh

@@ -1,22 +1,24 @@
-#!/usr/bin/env sh
+#!/usr/bin/env bash
 
 # Finds the last k0s releases of the given versions and generates json MATRIX_OUTPUT for github actions.
 # Usage:
 #  ./gen-matrix.sh 1.24.2 1.24.3
 # Output: ["v1.24.2+k0s.0", "v1.24.3+k0s.0"]
 
+set -e -o pipefail
+
 list_k0s_releases() {
-  gh api -X GET /repos/k0sproject/k0s/releases \
-    -F per_page=100 --paginate \
-    --jq '.[] | select(.prerelease == false and .draft == false) | .name'
+  # shellcheck disable=SC2016
+  local query='.[] | select(.prerelease == false and .draft == false) | .name | select(startswith($ENV.VERSION_PREFIX))'
+  VERSION_PREFIX="v$1" gh api -X GET /repos/k0sproject/k0s/releases -F per_page=100 --paginate --jq "$query"
 }
 
 k0s_sort() {
   go run github.com/k0sproject/version/cmd/k0s_sort@v0.2.2
 }
 
 latest_release() {
-  list_k0s_releases | grep -F "v$1" | k0s_sort | tail -1
+  list_k0s_releases "$1" | k0s_sort | tail -1
 }
 
 json_print_latest_releases() {