CheckConnectionTask: Fix log level of database connection check logs

When the plugin is used with default connection timeout (1000ms),
the "Checking database connection" message is emitted to the log
at level "info" every second. Reduce the level to debug.

The "Problem checking database connection" message is only emitted
at debug level, meaning in most installations it will not be seen.
Increase the level to error.

Change-Id: Iae48e56929b94857bdabdc0891440ebed1f69e72
diff --git a/src/main/java/com/ericsson/gerrit/plugins/eventslog/sql/SQLStore.java b/src/main/java/com/ericsson/gerrit/plugins/eventslog/sql/SQLStore.java
index 9be05fd..4947f78 100644
--- a/src/main/java/com/ericsson/gerrit/plugins/eventslog/sql/SQLStore.java
+++ b/src/main/java/com/ericsson/gerrit/plugins/eventslog/sql/SQLStore.java
@@ -274,12 +274,12 @@
     }
 
     private boolean checkConnection() {
-      log.info("Checking database connection...");
+      log.debug("Checking database connection...");
       try {
         eventsDb.queryOne();
         return true;
       } catch (SQLException e) {
-        log.debug("Problem checking database connection", e);
+        log.error("Problem checking database connection", e);
         return false;
       }
     }