Replace deprecated SDL APIs

Replace deprecated SDL SdlInstance usage with xapp-frame's SdlStorage
APIs, which have been built on top of the valid SDL SyncStorage APIs.
Upgrade SDL version to v0.8.0.
Bump appmgr's Docker container tag to 0.5.4.

Issue-Id: RIC-805

Signed-off-by: Timo Tietavainen <timo.tietavainen@nokia.com>
Change-Id: Ib68a380544fd75e31ca99d74bd319eae9f029aee
7 files changed