core: fix memory leak in transient units ยท lnykryn/systemd-rhel@fdee638

Fixes: ==1== HEAP SUMMARY: ==1== in use at exit: 67,182 bytes in 91 blocks ==1== total heap usage: 70,485 allocs, 70,394 frees, 42,184,635 bytes allocated ==1== ==1== 5,742 (696 direct, 5,046...