Increase leadership election timeout to 2500ms

Change-Id: I824fe2b56caeb344f65cfccaf54d8cf3fcafb49b
(cherry picked from commit 8825b4baf4445609819086685a62064ade23ff66)
diff --git a/core/store/dist/src/main/java/org/onosproject/store/cluster/impl/DistributedLeadershipStore.java b/core/store/dist/src/main/java/org/onosproject/store/cluster/impl/DistributedLeadershipStore.java
index c3a3977..fdecf31 100644
--- a/core/store/dist/src/main/java/org/onosproject/store/cluster/impl/DistributedLeadershipStore.java
+++ b/core/store/dist/src/main/java/org/onosproject/store/cluster/impl/DistributedLeadershipStore.java
@@ -87,7 +87,7 @@
     @Reference(cardinality = ReferenceCardinality.MANDATORY_UNARY)
     protected UpgradeService upgradeService;
 
-    private static final long DEFAULT_ELECTION_TIMEOUT_MILLIS = 250;
+    private static final long DEFAULT_ELECTION_TIMEOUT_MILLIS = 2500;
     @Property(name = "electionTimeoutMillis", longValue = DEFAULT_ELECTION_TIMEOUT_MILLIS,
             label = "the leader election timeout in milliseconds")
     private long electionTimeoutMillis = DEFAULT_ELECTION_TIMEOUT_MILLIS;