Support of several VNF and VDU in ns-heal and vnf-heal commands

Click does not allow advanced patterns for positional options.
This makes impossible to request the healing of several VNF or VDU
with different options like --count-index or --run-day1.

This change introduces a processing of the args used in ns-heal and
vnf-heal commands to allow those patterns.

In addition, the change introduces the logic to use either the VNF
instance ID or the identifier of a VNF inside a NS, known as
"member-vnf-index-ref".

Change-Id: I8b2f18aff6146ce579da33e67054f4a0f98c706a
Signed-off-by: garciadeblas <gerardo.garciadeblas@telefonica.com>