BibIndex: clean warning messages in test suite

* Mutes warnings caused by SQL DROP TABLE query.  (closes #1615)

* Fix for improper use of search_unit_in_bibrec function
  inside WordTable class.

Signed-off-by: Grzegorz Szpura <grzegorz.szpura@cern.ch>
Reviewed-by: Tibor Simko <tibor.simko@cern.ch>
errorlib: wrap warnings to invenio.err

* Redirects captured warnings and corresponding
  tracebacks directly into invenio.err rather
  than polluting stderr and consequently apache.err.
  (closes #1616)

Signed-off-by: Samuele Kaplun <samuele.kaplun@cern.ch>
Tested-by: Tibor Simko <tibor.simko@cern.ch>
BibUpload: pretend holding pen fix

* Correctly apply pretend mode when inserting
  into the holding pen.  (closes #1618)

Signed-off-by: Samuele Kaplun <samuele.kaplun@cern.ch>
Tested-by: Tibor Simko <tibor.simko@cern.ch>
BibCirculation: minor spelling error fix

Reviewed-by: Tibor Simko <tibor.simko@cern.ch>