db: keep in_transaction as a counter, so we can nest commits.

Otherwise we find ourselves outside a commitment.  This is a bandaid
until we remove nested commitments again at the end of this series.

Signed-off-by: Rusty Russell <rusty@rustcorp.com.au>

wallet/db.c

@@ -235,6 +235,7 @@ bool db_begin_transaction(struct db *db)
 		assert(db->in_transaction);
 		return db->in_transaction;
 	}
+	db->in_transaction++;
 	return false;
 }
 
@@ -242,7 +243,7 @@ bool db_commit_transaction(struct db *db)
 {
 	assert(db->in_transaction);
 	bool ret = db_exec(__func__, db, "COMMIT;");
-	db->in_transaction = false;
+	db->in_transaction--;
 	return ret;
 }
 
@@ -250,7 +251,7 @@ bool db_rollback_transaction(struct db *db)
 {
 	assert(db->in_transaction);
 	bool ret = db_exec(__func__, db, "ROLLBACK;");
-	db->in_transaction = false;
+	db->in_transaction--;
 	return ret;
 }
 

wallet/db.h

@@ -15,7 +15,7 @@
 
 struct db {
 	char *filename;
-	bool in_transaction;
+	unsigned int in_transaction;
 	const char *err;
 	sqlite3 *sql;
 };