set view argument for vim.interlace.rmd

When building a pdf from rmd, the pdf is currently opened even if g:vimrplugin_openpdf is set to 0.  I just copied the relevant code from rnw_rplugin.vim to rmd_rplugin.vim so that g:vimrplugin_openpdf is now respected.  I don't use rrst but I think that the same issue might be present there.