transaction: introduce transaction_abort_and_free()

Will be used in following commits.

src/core/transaction.c

@@ -1208,3 +1208,12 @@ Transaction *transaction_free(Transaction *tr) {
 
         return mfree(tr);
 }
+
+Transaction *transaction_abort_and_free(Transaction *tr) {
+        if (!tr)
+                return NULL;
+
+        transaction_abort(tr);
+
+        return transaction_free(tr);
+}

src/core/transaction.h

@@ -17,6 +17,8 @@ struct Transaction {
 
 Transaction *transaction_new(bool irreversible);
 Transaction *transaction_free(Transaction *tr);
+Transaction *transaction_abort_and_free(Transaction *tr);
+DEFINE_TRIVIAL_CLEANUP_FUNC(Transaction*, transaction_abort_and_free);
 
 void transaction_add_propagate_reload_jobs(Transaction *tr, Unit *unit, Job *by, bool ignore_order, sd_bus_error *e);
 int transaction_add_job_and_dependencies(