[install] Update diagrams for Mitaka

Update diagrams for Mitaka including addition of
the Shared File System service and increasing
size to improve readability. Also update Block
Storage node description in overview to include
Shared File System service.

Change-Id: I4ed900f5c9d6b03cb14aceb1e73e4629d4ee33aa
Implements: bp installguide-mitaka

doc/install-guide/source/overview.rst

@@ -163,7 +163,7 @@ Block Storage
 -------------
 
 The optional Block Storage node contains the disks that the Block
-Storage service provisions for instances.
+Storage and Shared File System services provision for instances.
 
 For simplicity, service traffic between compute nodes and this node
 uses the management network. Production environments should implement