Fix fake SDL database backend to support multiple set calls

Old fake SDL database backend implementation overwrote the whole fake
database (dictionary) with new key-values what were given in set() API
call. Fixed this to append received key-values in a set() API call to
the old values in the dictionary.

Signed-off-by: Timo Tietavainen <timo.tietavainen@nokia.com>
Change-Id: I8000ed86a1976951270c40d4d2358077ecc3785b
diff --git a/docs/release-notes.rst b/docs/release-notes.rst
index 8951370..c7b927d 100644
--- a/docs/release-notes.rst
+++ b/docs/release-notes.rst
@@ -33,7 +33,7 @@
 Version history
 ---------------
 
-[2.0.1] - 2020-01-08
+[2.0.1] - 2020-01-13
 
 * Add a fake database backend implementation to be used only for testing
   purposes when the real DBAAS database service is not available.