test: add missing BeforeClass import

Author: Surya Srinivasan

server/src/test/java/com/cloud/user/AccountManagerImplTest.java

@@ -47,6 +47,7 @@
 import org.apache.cloudstack.resourcedetail.UserDetailVO;
 import org.apache.cloudstack.webhook.WebhookHelper;
 import org.junit.Assert;
+import org.junit.BeforeClass;
 import org.junit.Before;
 import org.junit.Test;
 import org.junit.runner.RunWith;