Due to a known bug in zfs, renaming a BE can fail if the BE has
a dependent clone that is currently mounted or otherwise busy.

For example, after successfully upgrading the live boot environment,
attempting to rename the upgraded BE that was automatically generated
fails because it is has been activated and the live boot environment
is now its clone.

# 
# beadm list

BE          Active Active on Mountpoint Space 
Name               reboot               Used 
----        ------ --------- ---------- -----
opensolaris yes    yes       legacy     2.29G
# 
# 
# pkg -s http://ipkg.sfbay:80 image-update
DOWNLOAD                                    PKGS       FILES     XFER (MB)
Completed                                    4/4         3/3     1.24/1.24 

PHASE                                        ACTIONS
Update Phase                                   13/13 
A clone of opensolaris exists and has been updated and activated.  On next boot
the Boot Environment opensolaris-1 will be mounted on '/'. Reboot when ready to
switch to this updated BE.

# 
# 
# beadm list

BE            Active Active on Mountpoint Space 
Name                 reboot               Used 
----          ------ --------- ---------- -----
opensolaris-1 no     yes       -          2.29G
opensolaris   yes    no        legacy     0
# 
# 
# beadm rename opensolaris-1 myBE
beadm: rename of BE: opensolaris-1 failed
# 
# 



A workaround to this is to:

1. activate the live BE.
2. rename the upgrade BE.
3. activate the upgraded BE.

# 
# beadm activate opensolaris
# 
# beadm rename opensolaris-1 myBE
# 
# beadm activate myBE
#