Running solvent in MPI doesn't change the update, and cant converge

[Gabrielgerez]

While running calculations for #458 I found out that in both the master version of the code and in the newer version from #458 running Solvent in MPI does not work. One of the issues is handled in #458 (clear method is breaking), but there is a second one which I havent found out. the update of the reaction potential is never updated (?) and therefore the potential does not stop iterating. This is not an issue when running on omp only.