prevent loop when adding metacontact to roster
(fixes #1953 and maybe #1991)
merging with r6314
merging r6308
merged r6263
merge r6270
merge r6276
merge r6279
merge r6294
merge r6295
merge r6301
merge r6311
merge r6323
merge r6331
merge r6335
merge r6342
merge r6346
merge r6348
merge r6349
merge r6360
merge r6362