server: enable KVM volume and VM snapshot by default

Given EL6/EL7 is deprecated now and most modern supported KVM distros
ship newer versions of qemu, KVM volume and VM snapshot can be enabled
by default.

Fixes #11445

Signed-off-by: Rohit Yadav <rohit.yadav@shapeblue.com>

Author: yadvr

server/src/main/java/com/cloud/configuration/Config.java

@@ -405,7 +405,7 @@ public enum Config {
             "300",
             "The time interval in seconds when the management server polls for snapshots to be scheduled.",
             null),
-    KVMSnapshotEnabled("Hidden", SnapshotManager.class, Boolean.class, "kvm.snapshot.enabled", "false", "Whether volume snapshot is enabled on running instances on a KVM host", null),
+    KVMSnapshotEnabled("Hidden", SnapshotManager.class, Boolean.class, "kvm.snapshot.enabled", "true", "Whether volume snapshot is enabled on running instances on a KVM host", null),
 
     // Advanced
     EventPurgeInterval(

server/src/main/java/com/cloud/storage/snapshot/SnapshotManager.java

@@ -53,7 +53,7 @@ public interface SnapshotManager extends Configurable {
     public static final ConfigKey<Integer> BackupRetryInterval = new ConfigKey<Integer>(Integer.class, "backup.retry.interval", "Advanced", "300",
             "Time in seconds between retries in backing up snapshot to secondary", false, ConfigKey.Scope.Global, null);
 
-    public static final ConfigKey<Boolean> VmStorageSnapshotKvm = new ConfigKey<>(Boolean.class, "kvm.vmstoragesnapshot.enabled", "Snapshots", "false", "For live snapshot of virtual machine instance on KVM hypervisor without memory. Requires qemu version 1.6+ (on NFS or Local file system) and qemu-guest-agent installed on guest VM", true, ConfigKey.Scope.Global, null);
+    public static final ConfigKey<Boolean> VmStorageSnapshotKvm = new ConfigKey<>(Boolean.class, "kvm.vmstoragesnapshot.enabled", "Snapshots", "true", "For live snapshot of virtual machine instance on KVM hypervisor without memory. Requires qemu version 1.6+ (on NFS or Local file system) and qemu-guest-agent installed on guest VM", true, ConfigKey.Scope.Global, null);
 
     ConfigKey<Boolean> kvmIncrementalSnapshot = new ConfigKey<>(Boolean.class, "kvm.incremental.snapshot", "Snapshots", "false", "Whether differential snapshots are enabled for" +
             " KVM or not. When this is enabled, all KVM snapshots will be incremental. Bear in mind that it will generate a new full snapshot when the snapshot chain reaches the limit defined in snapshot.delta.max.", true, ConfigKey.Scope.Cluster, null);