This changes the lpsolver test to explicitly test the available
linear solvers we have - either CoinMP, LpSolver or both. This
prevents that a newly added solver will be automatically tested
as it can have a different behaviour for the tested input values.

Change-Id: I0c4d2f9c561d1e834ca51196b7b5ecf7d89ba550
Reviewed-on: https://gerrit.libreoffice.org/34813Tested-by: Jenkins <ci@libreoffice.org>
Reviewed-by: Tomaž Vajngerl <quikee@gmail.com>