scripts/spdkcli: Throw exception if syntax of the 'create' portal group command is incorrect.

Fixes #751

Change-Id: I6c73c563d32cf930c295b7058492a2344b38883d
Signed-off-by: Pawel Kaminski <pawelx.kaminski@intel.com>
Reviewed-on: https://review.gerrithub.io/c/spdk/spdk/+/451258
Tested-by: SPDK CI Jenkins <sys_sgci@intel.com>
Reviewed-by: Paweł Niedźwiecki <pawelx.niedzwiecki@intel.com>
Reviewed-by: Jim Harris <james.r.harris@intel.com>
Reviewed-by: Darek Stojaczyk <dariusz.stojaczyk@intel.com>

scripts/spdkcli/ui_node_iscsi.py

@@ -1,3 +1,4 @@
+from configshell_fb import ExecutionError
 from rpc.client import JSONRPCException
 from .ui_node import UINode
 
@@ -306,6 +307,9 @@ class UIPortalGroups(UINode):
             cpumask = None
             if "@" in portal:
                 host, cpumask = portal.split("@")
+            if ":" not in host:
+                raise ExecutionError("Incorrect format of portal group. Port is missing."
+                                     "Use 'help create' to see the command syntax.")
             host, port = host.rsplit(":", -1)
             portals.append({'host': host, 'port': port})
             if cpumask: