Code error in cephutils.py, causes problem with live migrations

[nickmdg]

There is a small spelling error in cephutils.py where self is miss spelt as 'slef' this error looks to only trigger during a SXM migration.

453c453
<         util.pread2(["dmsetup", "create", slef.DM_MIRROR_NAME, "--table", "0 %s snapshot %s %s P 1" % (str(int(size) / 512), self.DM_ZERO_DEV, self.RBD_SXM_MIRROR_DEV)])

---
>         util.pread2(["dmsetup", "create", self.DM_MIRROR_NAME, "--table", "0 %s snapshot %s %s P 1" % (str(int(size) / 512), self.DM_ZERO_DEV, self.RBD_SXM_MIRROR_DEV)])

[rposudnevskiy]

Thank you. Fixed.