Create websessions folder at instantiation

When the plugin started and no websessions folder was present in the
gerrit site, an error message was logged. The folder was created after.

Create the websessions folder at instantiation time and change the log
level to info.

Change-Id: Id1b408bcd38adbcdeb40eb7ea6d3e9277e5046f2

src/main/java/com/googlesource/gerrit/plugins/websession/flatfile/FlatFileWebSessionCache.java

diff --git a/src/main/java/com/googlesource/gerrit/plugins/websession/flatfile/FlatFileWebSessionCache.java b/src/main/java/com/googlesource/gerrit/plugins/websession/flatfile/FlatFileWebSessionCache.java
index 11e5b78..1f32053 100644
--- a/src/main/java/com/googlesource/gerrit/plugins/websession/flatfile/FlatFileWebSessionCache.java
+++ b/src/main/java/com/googlesource/gerrit/plugins/websession/flatfile/FlatFileWebSessionCache.java
@@ -59,7 +59,8 @@
     dir = new File(cfg.getFromGerritConfig("websession-flatfile")
         .getString("directory", site.site_path + "/websessions"));
     if (!dir.exists()) {
-      log.error(dir.getAbsolutePath() + " not found");
+      log.info(dir + " not found. Creating it.");
+      dir.mkdir();
     }
   }
 
@@ -147,10 +148,6 @@
 
   @Override
   public void put(String key, Val value) {
-    if (!dir.exists()) {
-      dir.mkdir();
-    }
-
     File tempFile = null;
     OutputStream fileStream = null;
     ObjectOutputStream objStream = null;