LVM segfault issue

[cholcombe973]

With enough threads it seems that LVM init segfaults for some unknown reason.
```00:16:10 [DEBUG] postgres: preparing query with name ``: UPDATE hardware SET state = 'unscanned' WHERE device_id=2
00:16:10 [DEBUG] postgres: executing query: COMMIT
00:16:10 [DEBUG] bynar::test_disk: thread 2993564 Transition failed. Trying next transition
00:16:10 [DEBUG] lvm: dropping lvm

Thread 28 "bynar" received signal SIGSEGV, Segmentation fault.
[Switching to Thread 0x7fffe33f9700 (LWP 2993637)]
0x00007ffff7683607 in dm_pool_alloc_aligned () from /lib/x86_64-linux-gnu/libdevmapper.so.1.02.1
(gdb) bt
#0 0x00007ffff7683607 in dm_pool_alloc_aligned () from /lib/x86_64-linux-gnu/libdevmapper.so.1.02.1
#1 0x00007ffff7683a5e in dm_pool_zalloc () from /lib/x86_64-linux-gnu/libdevmapper.so.1.02.1
#2 0x00007ffff78cef48 in ?? () from /lib/x86_64-linux-gnu/liblvm2app.so.2.2
#3 0x00007ffff78c3cae in ?? () from /lib/x86_64-linux-gnu/liblvm2app.so.2.2
#4 0x00007ffff78c755e in ?? () from /lib/x86_64-linux-gnu/liblvm2app.so.2.2
#5 0x00007ffff78b46a0 in lvm_init () from /lib/x86_64-linux-gnu/liblvm2app.so.2.2
#6 0x0000555556284acc in lvm::Lvm::new::h70e76aef47c8d063 (system_dir=Option<&str>) at lvm/src/lib.rs:450
#7 0x0000555555c2a5b0 in bynar::test_disk::is_disk_blank::h6e8f871b18876247 (dev=0x7fff74001320) at src/test_disk.rs:1586
#8 0x0000555555c19802 in _$LT$bynar..test_disk..Eval$u20$as$u20$bynar..test_disk..Transition$GT$::transition::h985d5930d2e53f8b (
to_state=Good, device=0x7fffe33f2d48, _scsi_info=0x7fffe33f2ed8, _simulate=false) at src/test_disk.rs:449

[cholcombe973]

A workaround has been implemented in #63

[sdandam]

This seems to be an issue with the DB transaction failing with multiple-threads?

[cholcombe973]

https://bugzilla.redhat.com/show_bug.cgi?id=851287 It looks like this was never meant to be used in a multithreaded context. There's a few possible workarounds for this:

1. Wrap the LVM struct in an Arc
2. Do one global lvm list and pass that to the state machines
3. ??