Help message of heal cli modified

Usage message of all cli commands of tacker is constructed by
argument parser by default. It includes optional parameter
first and insert mandatory parameter at end.

All cli commands are implemented with this design only
except heal cli.

Heal cli is a special case in which optional parameter is
coming at end and mandatory parameter is coming before optional.
To fix this issue usage parameter of argument parser is set
in heal cli.

Closes-Bug: #1954744

Change-Id: I3b1d04df210ad07d4b9a99f300017d49e2b56f0b

tackerclient/osc/v1/vnflcm/vnflcm.py

@@ -238,6 +238,11 @@ class HealVnfLcm(command.Command):
 
     def get_parser(self, prog_name):
         parser = super(HealVnfLcm, self).get_parser(prog_name)
+        usage_message = ('''%(prog)s [-h] [--cause CAUSE]
+                             [--vnfc-instance <vnfc-instance-id> '''
+                         '''[<vnfc-instance-id> ...]]
+                             -- <vnf-instance>''')
+        parser.usage = usage_message
         parser.add_argument(
             _VNF_INSTANCE,
             metavar="<vnf-instance>",