tests/btrfs.c: do not use alloca
tests/btrfs.c: do not use alloca

* tests/btrfs.c: Don't include <alloca.h>.
(btrfs_test_subvol_ioctls): Allocate
struct btrfs_ioctl_vol_args_v2.qgroup_inherit using tail_alloc.

cuviper/strace,Saruta/strace,cuviper/strace,Saruta/strace,cuviper/strace,Saruta/strace,Saruta/strace,cuviper/strace,cuviper/strace,Saruta/strace