Adds alternate credentials for alternate projects (GoogleCloudPlatform#774)

Author: bshaffer

.kokoro/php56.cfg

@@ -6,8 +6,12 @@ env_vars: {
     value: "gcr.io/cloud-devrel-kokoro-resources/php56"
 }
 
-# Give the docker image a unique project ID per PHP version
+# Give the docker image a unique project ID and credentials per PHP version
 env_vars: {
     key: "GOOGLE_ALT_PROJECT_ID"
     value: "php-docs-samples-php56"
 }
+env_vars: {
+    key: "GOOGLE_ALT_CREDENTIALS_FILENAME"
+    value: "service-account-php56.json"
+}

.kokoro/php70.cfg

@@ -6,8 +6,12 @@ env_vars: {
     value: "gcr.io/cloud-devrel-kokoro-resources/php70"
 }
 
-# Give the docker image a unique project ID per PHP version
+# Give the docker image a unique project ID and credentials per PHP version
 env_vars: {
     key: "GOOGLE_ALT_PROJECT_ID"
     value: "php-docs-samples-php70"
 }
+env_vars: {
+    key: "GOOGLE_ALT_CREDENTIALS_FILENAME"
+    value: "service-account-php70.json"
+}

.kokoro/php71.cfg

@@ -6,8 +6,12 @@ env_vars: {
     value: "gcr.io/cloud-devrel-kokoro-resources/php71"
 }
 
-# Give the docker image a unique project ID per PHP version
+# Give the docker image a unique project ID and credentials per PHP version
 env_vars: {
     key: "GOOGLE_ALT_PROJECT_ID"
     value: "php-docs-samples-php71"
 }
+env_vars: {
+    key: "GOOGLE_ALT_CREDENTIALS_FILENAME"
+    value: "service-account-php71.json"
+}

.kokoro/php72.cfg

@@ -6,8 +6,12 @@ env_vars: {
     value: "gcr.io/cloud-devrel-kokoro-resources/php72"
 }
 
-# Give the docker image a unique project ID per PHP version
+# Give the docker image a unique project ID and credentials per PHP version
 env_vars: {
     key: "GOOGLE_ALT_PROJECT_ID"
     value: "php-docs-samples-php72"
 }
+env_vars: {
+    key: "GOOGLE_ALT_CREDENTIALS_FILENAME"
+    value: "service-account-php72.json"
+}

.kokoro/secrets.sh.enc

@@ -20,6 +20,8 @@ set -ex
 cd github/php-docs-samples
 
 export GOOGLE_APPLICATION_CREDENTIALS=$KOKORO_GFILE_DIR/service-account.json
+export GOOGLE_ALT_APPLICATION_CREDENTIALS=$KOKORO_GFILE_DIR/$GOOGLE_ALT_CREDENTIALS_FILENAME
+
 export PATH="$PATH:/opt/composer/vendor/bin:/root/google-cloud-sdk/bin"
 
 # export the secrets

.kokoro/system_tests.sh

@@ -1,2 +1,3 @@
 # Modify this file with whitespace in a PR in order to run all tests for the PR.
 # See "testing/run_test_suite.sh" for more details.
+# 

testing/RUN_ALL_TESTS

@@ -87,7 +87,11 @@ run_tests()
     fi
     if [[ "${ALT_PROJECT_TESTS[@]}" =~ "${DIR}" ]] && [ ! -z "$GOOGLE_ALT_PROJECT_ID" ]; then
         echo "Using alternate project $GOOGLE_ALT_PROJECT_ID"
-        GCLOUD_PROJECT=$GOOGLE_ALT_PROJECT_ID GOOGLE_PROJECT_ID=$GOOGLE_ALT_PROJECT_ID GOOGLE_STORAGE_BUCKET=$GOOGLE_ALT_STORAGE_BUCKET $CMD
+        GOOGLE_APPLICATION_CREDENTIALS=$GOOGLE_ALT_APPLICATION_CREDENTIALS \
+            GCLOUD_PROJECT=$GOOGLE_ALT_PROJECT_ID \
+            GOOGLE_PROJECT_ID=$GOOGLE_ALT_PROJECT_ID \
+            GOOGLE_STORAGE_BUCKET=$GOOGLE_ALT_STORAGE_BUCKET \
+            $CMD
     else
         $CMD
     fi