Update descriptions for VM volume allocation algorithms

Update descriptions for VM volume allocation algorithms

Author: rajujith

source/adminguide/vm_volume_allocators.rst

@@ -40,10 +40,10 @@ VM allocator supports following algorithms to select a host in the cluster:
 Algorithm                      Description
 ============================= ========================
 random		                   Selects a host in the cluster randomly.
-firstfit		               Selects the first available host in the cluster.
-userdispersing	               Selects the host running least instances for the account, aims to spread out the instances belonging to a single user account.
-userconcentratedpod_random     Selects the host randomly aiming to keep all instances belonging to single user account in same pod.
-userconcentratedpod_firstfit   Selects the first suitable host from a pod running most instances for the user.
+firstfit		                   Selects the first available host in the cluster.
+userdispersing	                Selects the host running least instances for the account, aims to spread out the instances belonging to a single user account.
+userconcentratedpod_random     Behaves same as random algorithm.
+userconcentratedpod_firstfit   Behaves same as firstfit algorithm.
 firstfitleastconsumed          Selects the first host after sorting eligible hosts by least allocated resources (such as CPU or RAM).
 ============================= ========================