(ITS#6748) slapo-memberof can log scrambled error text

[h . b . furuseth]

Full_Name: Hallvard B Furuseth
Version: HEAD
OS: 
URL: 
Submission from: (NULL) (129.240.6.233)
Submitted by: hallvard


memberof_value_modify() calls
    op->o_bd->be_modify( &op2, &rs2 );
and then uses rs2.sr_text, which can be a value on be_modify's stack.

Fixing by deleting 'text=...' from the error message.