Simplified org-export pdf command

KJHealy's export script called latexmk in pdflatex mode with extra flags

latexmk -pdflatex='pdflatex -synctex=1 --shell-escape --' -pdf %f

I'm not sure why, but in 14.04 these extra pdflatex flags are screwing
up the export so I decided to go with the most simple latexmk command.