Clean up /etc/resolconf/resolv.conf.d files

resolvconf populates /etc/resolv.conf from files in /etc/resolvconf/resolv.conf.d
Make sure to clean up these files at the end of stemcell build

Signed-off-by: Maria Shaldibina <mariash@pivotallabs.com>
Bump go-agent

Signed-off-by: Maria Shaldibina <mariash@pivotallabs.com>