server: Fix volume.stats.interval description (#3415)

Tested manually - value is in miliseconds, not seconds for the setting volume.stats.interval

Author: andrijapanicsb

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

@@ -849,7 +849,7 @@ public enum Config {
             "The interval (in milliseconds) when vm stats are retrieved from agents.",
             null),
     VmDiskStatsInterval("Advanced", ManagementServer.class, Integer.class, "vm.disk.stats.interval", "0", "Interval (in seconds) to report vm disk statistics.", null),
-    VolumeStatsInterval("Advanced", ManagementServer.class, Integer.class, "volume.stats.interval", "60000", "Interval (in seconds) to report volume statistics.", null),
+    VolumeStatsInterval("Advanced", ManagementServer.class, Integer.class, "volume.stats.interval", "60000", "Interval (in miliseconds) to report volume statistics.", null),
     VmTransitionWaitInterval(
             "Advanced",
             ManagementServer.class,