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
diff --git a/go.mod b/go.mod
index 6c1b108..71eeb8b 100644
--- a/go.mod
+++ b/go.mod
@@ -2,7 +2,7 @@
 
 go 1.12
 
-replace gerrit.o-ran-sc.org/r/ric-plt/sdlgo => gerrit.o-ran-sc.org/r/ric-plt/sdlgo.git v0.7.0
+replace gerrit.o-ran-sc.org/r/ric-plt/sdlgo => gerrit.o-ran-sc.org/r/ric-plt/sdlgo.git v0.8.0
 
 replace gerrit.o-ran-sc.org/r/com/golog => gerrit.o-ran-sc.org/r/com/golog.git v0.0.2