Update CHANGELOG to fix BUG FIXES of release 3.1.2

Author: francesco-giordano

CHANGELOG.md

@@ -7,8 +7,8 @@ This file is used to list changes made in each version of the AWS ParallelCluste
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 **BUG FIXES**
-- Fix update of `/etc/hosts` files for clusters deployed in VPC without internet access.
-- Wait for ephemeral drives setup before having a compute node join the scheduler.
+- Fix the update of `/etc/hosts` file on computes nodes when a cluster is deployed in subnets without internet access.
+- Fix compute nodes bootstrap by waiting for ephemeral drives initialization before joining the cluster.
 
 3.1.0
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