AuthHealthCheck: evict account cache by username

Make sure to trigger the entire auth stack by evicting
the in-memory account cache for the healthcheck user.

Checking the auth by relying on the cache would not highlight
potential problems related to new users trying to sign up or
existing users logging it after a period of inactivity long
enough to allow the in-memory cache of its accountState to expire.

Change-Id: Ied4b77aeaaf3f064f22815c3582713b24f36b942
diff --git a/src/main/java/com/googlesource/gerrit/plugins/healthcheck/check/AuthHealthCheck.java b/src/main/java/com/googlesource/gerrit/plugins/healthcheck/check/AuthHealthCheck.java
index 4003351..be17e74 100644
--- a/src/main/java/com/googlesource/gerrit/plugins/healthcheck/check/AuthHealthCheck.java
+++ b/src/main/java/com/googlesource/gerrit/plugins/healthcheck/check/AuthHealthCheck.java
@@ -55,6 +55,7 @@
     authRequest.setPassword(password);
     realm.authenticate(authRequest);
 
+    byIdCache.evictByUsername(username);
     AccountState accountState = byIdCache.getByUsername(username);
     if (accountState == null) {
       log.error("Cannot load account state for username " + username);