fix devel jobs not handling ros/catkin#639 well with the changed working directory

Working: http://jenkins.ros.org/job/devel-hydro-octomap/13/ARCH_PARAM=amd64,UBUNTU_PARAM=precise,label=devel/console

Broking: http://jenkins.ros.org/job/devel-hydro-octomap/15/ARCH_PARAM=amd64,UBUNTU_PARAM=precise,label=devel/console

The install location has changed since catkin_make_isolated is using `PWD` now which is not set correctly when the buildfarm script changes `cwd`.

@tfoote FYI