Check all invocations of pcn_kmsg_done for correct usage

[bxatnarf]

pcn_kmsg_done(void *msg) assumes that its argument is a valid pointer to a (malloc'd) struct pcn_kmsg_hdr. This is not the case in all invocations, e.g., issue #63. We need to hunt down and patch any remaining buggy invocations.

List of call sites to check:

1. kernel/popcorn/remote_info.c:293: pcn_kmsg_done(res);
2. kernel/popcorn/remote_info.c:332: pcn_kmsg_done(response);
3. kernel/popcorn/page_server.c:819: pcn_kmsg_done(req);
4. kernel/popcorn/page_server.c:914: pcn_kmsg_done(res);
5. kernel/popcorn/page_server.c:1142: pcn_kmsg_done(rp);
6. kernel/popcorn/page_server.c:1730: pcn_kmsg_done(rp);
7. kernel/popcorn/vma_server.c:268: pcn_kmsg_done(res);
8. kernel/popcorn/vma_server.c:294: pcn_kmsg_done(res);
9. kernel/popcorn/vma_server.c:314: pcn_kmsg_done(res);
10. kernel/popcorn/vma_server.c:338: pcn_kmsg_done(res);
11. kernel/popcorn/vma_server.c:362: pcn_kmsg_done(res);
12. kernel/popcorn/vma_server.c:405: pcn_kmsg_done(res);
13. kernel/popcorn/vma_server.c:548: pcn_kmsg_done(req);
14. kernel/popcorn/vma_server.c:605: pcn_kmsg_done(res);
15. kernel/popcorn/vma_server.c:672: pcn_kmsg_done(req);
16. kernel/popcorn/vma_server.c:830: pcn_kmsg_done((void *)vi->response);
17. kernel/popcorn/bundle.c:94: pcn_kmsg_done(msg);
18. kernel/popcorn/process_server.c:212: pcn_kmsg_done(res);
19. kernel/popcorn/process_server.c:256: pcn_kmsg_done(req);
20. kernel/popcorn/process_server.c:362: pcn_kmsg_done(req);
21. kernel/popcorn/process_server.c:374: pcn_kmsg_done(req);
22. kernel/popcorn/process_server.c:390: pcn_kmsg_done(req);
23. kernel/popcorn/process_server.c:424: pcn_kmsg_done(req);
24. kernel/popcorn/process_server.c:498: pcn_kmsg_done(req);
25. kernel/popcorn/process_server.c:556: pcn_kmsg_done(req);
26. kernel/popcorn/process_server.c:847: pcn_kmsg_done(req);
27. kernel/popcorn/sched_server.c:90: pcn_kmsg_done(req);
28. kernel/popcorn/sched_server.c:191: pcn_kmsg_done(res);
29. kernel/popcorn/pcn_kmsg.c:70: pcn_kmsg_done(msg);
30. msg_layer/dolphin/msg_dolphin.c:793: pcn_kmsg_done(pcn_msg);
31. msg_layer/dolphin/msg_dolphin.c:816: pcn_kmsg_done(pcn_msg);
32. msg_layer/dolphin/msg_dolphin.c:927: pcn_kmsg_done(pcn_msg);
33. msg_layer/dolphin/msg_dolphin.c:936: pcn_kmsg_done(pcn_msg);
34. msg_layer/msg_test.c:148: pcn_kmsg_done(inc_lmsg);
35. msg_layer/msg_test.c:256: pcn_kmsg_done(act_buf);
36. msg_layer/msg_test.c:408: pcn_kmsg_done(res);
37. msg_layer/ib.c:1615: pcn_kmsg_done(req);
38. msg_layer/ib.c:1623: pcn_kmsg_done(res);