Add docker-compose based test fixture for Azure (#48636)

This commit adds a new :test:fixtures:azure-fixture project which 
provides a docker-compose based container that runs a AzureHttpFixture 
Java class that emulates an Azure Storage service.

The logic to emulate the service is extracted from existing tests and 
placed in AzureHttpHandler into the new project so that it can be 
easily reused. The :plugins:repository-azure project is an example 
of such utilization.

The AzureHttpFixture fixture is just a wrapper around AzureHttpHandler 
and is now executed within the docker container. 

The :plugins:repository-azure:qa:microsoft-azure project uses the new 
test fixture and the existing AzureStorageFixture has been removed.

plugins/repository-azure/build.gradle

@@ -27,6 +27,7 @@ dependencies {
   compile 'com.microsoft.azure:azure-keyvault-core:1.0.0'
   compile 'com.google.guava:guava:20.0'
   compile 'org.apache.commons:commons-lang3:3.4'
+  testCompile project(':test:fixtures:azure-fixture')
 }
 
 dependencyLicenses {

plugins/repository-azure/qa/microsoft-azure-storage/build.gradle

@@ -26,6 +26,9 @@ import static org.elasticsearch.gradle.PropertyNormalization.IGNORE_VALUE
 
 apply plugin: 'elasticsearch.standalone-rest-test'
 apply plugin: 'elasticsearch.rest-test'
+apply plugin: 'elasticsearch.test.fixtures'
+
+testFixtures.useFixture ":test:fixtures:azure-fixture", "azure-fixture"
 
 boolean useFixture = false
 
@@ -38,20 +41,12 @@ String azureSasToken = System.getenv("azure_storage_sas_token")
 if (!azureAccount && !azureKey && !azureContainer && !azureBasePath && !azureSasToken) {
     azureAccount = 'azure_integration_test_account'
     azureKey = 'YXp1cmVfaW50ZWdyYXRpb25fdGVzdF9rZXk=' // The key is "azure_integration_test_key" encoded using base64
-    azureContainer = 'container_test'
-    azureBasePath = 'integration_test'
+    azureContainer = 'container'
+    azureBasePath = ''
     azureSasToken = ''
     useFixture = true
 }
 
-/** A task to start the fixture which emulates an Azure Storage service **/
-task azureStorageFixture(type: AntFixture) {
-    dependsOn testClasses
-    env 'CLASSPATH', "${ -> project.sourceSets.test.runtimeClasspath.asPath }"
-    executable = new File(project.runtimeJavaHome, 'bin/java')
-    args 'org.elasticsearch.repositories.azure.AzureStorageFixture', baseDir, azureContainer
-}
-
 Map<String, Object> expansions = [
         'container': azureContainer,
         'base_path': azureBasePath + "_integration_tests"
@@ -77,11 +72,15 @@ testClusters.integTest {
     }
 
     if (useFixture) {
-        tasks.integTest.dependsOn azureStorageFixture
+        def azureAddress = {
+            int ephemeralPort = project(':test:fixtures:azure-fixture').postProcessFixture.ext."test.fixtures.azure-fixture.tcp.8091"
+            assert ephemeralPort > 0
+            'http://127.0.0.1:' + ephemeralPort
+        }
         // Use a closure on the string to delay evaluation until tests are executed. The endpoint_suffix is used
         // in a hacky way to change the protocol and endpoint. We must fix that.
         setting 'azure.client.integration_test.endpoint_suffix',
-                { "ignored;DefaultEndpointsProtocol=http;BlobEndpoint=http://${azureStorageFixture.addressAndPort }" }, IGNORE_VALUE
+                { "ignored;DefaultEndpointsProtocol=http;BlobEndpoint=${ -> azureAddress() }" }, IGNORE_VALUE
         String firstPartOfSeed = project.rootProject.testSeed.tokenize(':').get(0)
         setting 'thread_pool.repository_azure.max', (Math.abs(Long.parseUnsignedLong(firstPartOfSeed, 16) % 10) + 1).toString(), System.getProperty('ignore.tests.seed') == null ? DEFAULT : IGNORE_VALUE
     }