Fix current mapitest: module_zentyal

There were 2 issues executing `mapitest  --mapi-calls=ZENTYAL-ALL`:

* In 1863 `Administrator` user were being used (and normally this user won't have an openchange account), we can use the user from the profile which will have oc account acitvated for sure.
* 1872 test was giving sometime sigfaults because a bug (the original one) on nspi implementation
  * We were never setting `count` to 0, because `((ldb_res->count - r->in.pStat->NumPos) < 0)` is checking whether an `uint32_t` is < 0.
  * The test was sigfaulting because of `ldb_res->msgs[i+r->in.pStat->NumPos]` (NumPos is the faulty parameter we supply)
  * Besides we want to return an error instead of empty result and success result.
It is not blocker for merging but we should handle this case at some point. Therefore just a keep for reference, probably better fit as a github issue.