Don't manually add keys to the store

There is no need to preemptively add the keys to the store oneself.
SessionBuilder will take care of this for us. What's more, this will
prevent IdentityKeys from otherwise invalid bundles to show up in our
UI.

src/main/java/eu/siacs/conversations/crypto/axolotl/AxolotlService.java

@@ -536,8 +536,6 @@ public class AxolotlService {
 								bundle.getSignedPreKeyId(), bundle.getSignedPreKey(),
 								bundle.getSignedPreKeySignature(), bundle.getIdentityKey());
 
-						axolotlStore.saveIdentity(address.getName(), bundle.getIdentityKey());
-
 						try {
 							SessionBuilder builder = new SessionBuilder(axolotlStore, address);
 							builder.process(preKeyBundle);