You need to get the pifs again (or ideally, find the lines you used to change the mode in your bash history) – see here for getting pifs.
Then use the following:
xe pif-param-set uuid=bd26334f-f7ff-3206-e5b2-4c017c51907c other-config:bond-mode=balance-slb other-config:bond-updelay=200
This will set your bond back to balance-slb, and reduce the up-delay time (see here for the issue – although I can’t actually confirm right now that the issue still exists in XenServer 5.6, will try and find out and post here if I do*).
*ps, just doing cat /proc/net/bonding/bond0 will tell you.