Log the path that caused exception instead of websessions directory

Previously, failures while reading a websession file logged the
websessions directory, which was not helpful for identifying the
offending path.

Log the specific file path that triggered the exception instead, so that
it can be more easily investigated.

Bug: Issue 415076951
Change-Id: I4c292f0f9a5c42af617afdff67409f966c83e83c
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 0c52ce6..5f8016a 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
@@ -211,7 +211,7 @@
         log.atFine().withCause(e).log("Exception message %s", e.getMessage());
         invalidate(path.getFileName().toString());
       } catch (IOException e) {
-        log.atWarning().withCause(e).log("Cannot read cache %s", websessionsDir);
+        log.atWarning().withCause(e).log("Cannot read cache %s", path);
       }
     }
     return null;