After creating VNF Instance using vnflcm v1 API, tacker-horizon VNF
Manager tab becomes not being able to redner the view correctly. This
happens because VNF Manager tab tries to obtain `vim_name` and fails.
The `vim_name` attribute is no longer available in vnflcm v1 API.
This patch fix this problem by simply using `get` method to obtain
`vim_name`.
Closes-bug: #1950783
Signed-off-by: Hiromu Asahina <hiromu.asahina.az@hco.ntt.co.jp>
Change-Id: If78ffe41dbe3e04cde5678a07df9f55382eb5481