[horde] imsp_auth_user getting set to "imp"

[Liam Hoekenga]

I'm not sure why, but the default value of "imsp_auth_user" seems to be getting
set to "imp".. which, unsurprisingly, breaks Turba's ability to talk to the
IMSP server.

I've checked out horde/config/prefs.php, and imsp_auth_user's default value is
'', as is imsp_auth_pass's default value.  I've set them both to "locked" yet
it still lets me change the values.

Any ideas?  I'm using horde 3.0.1, imp 4.0.1, turba 2.0 and ingo 1.0

Liam