Add proper error messages on delete rApp response

Delete rApp provides the response based on the state of rApp and the existence of rApp instances.

Issue-ID: NONRTRIC-913
Signed-off-by: aravind.est <aravindhan.a@est.tech>
Change-Id: Ic9714a2e507e7c0a2035313ec3d3b6ee8bfddfdf
3 files changed