Decrypt all incoming OMEMO msg

Trust all key as long as it's for reading. This code isn't multithread
safe.

src/omemo/store.h

@@ -48,6 +48,7 @@ typedef struct {
    signal_buffer *private;
    uint32_t registration_id;
    GHashTable *trusted;
+   bool recv;
 } identity_key_store_t;
 
 GHashTable * session_store_new(void);