Mute warning when actions config file is missing

Actions config file is optional for its-* pluggins. Logging warning for
every plugin call cause noise in the logs.

Change-Id: Ide67be7b7181e02c3789532c30d41b9aafa56b50

src/main/java/com/googlesource/gerrit/plugins/its/base/workflow/RuleBase.java

diff --git a/src/main/java/com/googlesource/gerrit/plugins/its/base/workflow/RuleBase.java b/src/main/java/com/googlesource/gerrit/plugins/its/base/workflow/RuleBase.java
index b6e4ad6..fa96242 100644
--- a/src/main/java/com/googlesource/gerrit/plugins/its/base/workflow/RuleBase.java
+++ b/src/main/java/com/googlesource/gerrit/plugins/its/base/workflow/RuleBase.java
@@ -98,7 +98,7 @@
     Collection<Rule> fromProjectConfig = rulesProjectCache.get(projectName);
     Collection<Rule> rulesToAdd = !fromProjectConfig.isEmpty() ? fromProjectConfig : rules;
     if (rulesToAdd.isEmpty() && !globalRuleFile.exists() && !itsSpecificRuleFile.exists()) {
-      log.warn(
+      log.debug(
           "Neither global rule file {} nor Its specific rule file {} exist and no rules are "
               + "configured for project {}. Please configure rules.",
           globalRuleFile,