If users specify parameters in 'flavor' or 'image' properties
of a VDU, HOT template can not be processed properly because
there is a missmatch between TOSCA and HOT template.
This patch will change 'get_input' to 'get_param' to fix that
issue.
Change-Id: I353e9d9d70dc6249a62dcdd1281b7b60d28d7d30
Closes-Bug: #1813135
Depends-On: Ib95ed31c70073cb732d41defe5bdc8027eadfeec