Add ESX service cmd "version" (#2056)

This patch adds the command "version" to the ESX service so that VMDK
OPs VMs can send the command "version" to the VMCI socket and get back
the version of the ESX service running on the ESX host.

esx_service/vmdk_ops.py

@@ -22,13 +22,13 @@
 VMDK name is formed as [vmdatastore] dockvols/"Name".vmdk
 
 Commands ("cmd" in request):
-		"create" - create a VMDK in "[vmdatastore] dvol"
-		"remove" - remove a VMDK. We assume it's not open, and fail if it is
-		"list"   - enumerate VMDKs
-		"get"    - get info about an individual volume (vmdk)
-		"attach" - attach a VMDK to the requesting VM
-		"detach" - detach a VMDK from the requesting VM (assuming it's unmounted)
-
+		"create"  - create a VMDK in "[vmdatastore] dvol"
+		"remove"  - remove a VMDK. We assume it's not open, and fail if it is
+		"list"    - enumerate VMDKs
+		"get"     - get info about an individual volume (vmdk)
+		"attach"  - attach a VMDK to the requesting VM
+		"detach"  - detach a VMDK from the requesting VM (assuming it's unmounted)
+		"version" - get the ESX service version string
 '''
 
 import atexit
@@ -1827,8 +1827,13 @@ def execRequestThread(client_socket, cartel, request):
                 logging.warning("executeRequest '%s' failed: %s", req["cmd"], reply_string)
                 return
 
-            opts = req["details"]["Opts"] if "Opts" in req["details"] else {}
-            reply_string = executeRequest(
+            # If the command is "version" then there is no need to handle the request via
+            # the normal VM request handler.
+            if req["cmd"] == "version":
+                reply_string = {u'version': "%s" % vmdk_utils.get_version()}
+            else:
+                opts = req["details"]["Opts"] if "Opts" in req["details"] else {}
+                reply_string = executeRequest(
                                 vm_uuid=vm_uuid,
                                 vc_uuid=vc_uuid,
                                 vm_name=vm_name,