Added logback into GCP IT Module.

testing/indexer-test-gcp/src/test/resources/logback-test.xml

+<?xml version="1.0" encoding="UTF-8"?>
+<configuration>
+  <include resource="org/springframework/boot/logging/logback/defaults.xml"/>
+  <appender name="CONSOLE" class="ch.qos.logback.core.ConsoleAppender">
+    <encoder>
+      <pattern>%yellow([%thread]) %highlight(| %-5level |) %green(%d) %cyan(| %logger{15} |) %highlight(%msg) %n</pattern>
+      <charset>utf8</charset>
+    </encoder>
+  </appender>
+  <root level="INFO">
+    <appender-ref ref="CONSOLE" />
+  </root>
+</configuration>