Properly handle arguments and responses for triggering Docker builds. (#10545)

This moves the actual cURL command to a script, which both properly
handles the required parameters and also checks the results of the call
so that it throws an error if triggering the Docker build fails.

.travis.yml

@@ -361,12 +361,7 @@ jobs:
       after_failure: post_message "TRAVIS_MESSAGE" "<!here> Draft release submission failed"
 
     - name: Trigger Docker image build and publish
-      script: >-
-        curl -X POST \
-             -H 'Accept: application/vnd.github.v3+json' \
-             -H "Authorization: Bearer ${GITHUB_TOKEN}" \
-             'https://api.github.com/repos/netdata/netdata/actions/workflows/docker.yml/dispatches' \
-             -d '{"ref": "master", "inputs": {"version": "${build_version}"}}'
+      script: .travis/trigger_docker_build.sh "${GITHUB_TOKEN}" "${BUILD_VERSION}"
       after_failure: post_message "TRAVIS_MESSAGE" "<!here> Failed to trigger docker build during release" "${NOTIF_CHANNEL}"
 
     - stage: Trigger deb and rpm package build (release)
@@ -462,12 +457,7 @@ jobs:
       after_deploy: rm -f .travis/gcs-credentials.json
 
     - name: Trigger Docker image build and publish
-      script: >-
-        curl -X POST \
-             -H 'Accept: application/vnd.github.v3+json' \
-             -H "Authorization: Bearer ${GITHUB_TOKEN}" \
-             'https://api.github.com/repos/netdata/netdata/actions/workflows/docker.yml/dispatches' \
-             -d '{"ref": "master", "inputs": {"version": "${build_version}"}}'
+      script: .travis/trigger_docker_build.sh "${GITHUB_TOKEN}" "${BUILD_VERSION}"
       after_failure: post_message "TRAVIS_MESSAGE" "<!here> Failed to trigger docker build during nightly release" "${NOTIF_CHANNEL}"
 
     - stage: Trigger deb and rpm package build (nightly release)

.travis/trigger_docker_build.sh

@@ -0,0 +1,19 @@
+#!/bin/sh
+
+token="${0}"
+version="${1}"
+
+resp="$(curl -X POST \
+             -H 'Accept: application/vnd.github.v3+json' \
+             -H "Authorization: Bearer ${token}" \
+             "https://api.github.com/repos/netdata/netdata/actions/workflows/docker.yml/dispatches" \
+             -d "{\"ref\": \"master\", \"inputs\": {\"version\": \"${version}\"}}")"
+
+if [ -z "${resp}" ]; then
+    echo "Successfully triggered Docker image build."
+    exit 0
+else
+    echo "Failed to trigger Docker image build. Output:"
+    echo "${resp}"
+    exit 1
+fi