Local/ubstud/slowdown: Add sudo password loop

Every command should be executed here, or none at all. Enligtenment
follows in the next commit.

a176d978-b668-11e3-a89b-001f3b596ec9
Local/ubstud/slowdown: Show an additional diff about what happened

390fa0f2-b66a-11e3-bf32-001f3b596ec9
0d49819e-b66b-11e3-bf73-001f3b596ec9
Local/ubstud/slowdown: Only run on ubstud

00d32414-b66c-11e3-aa73-001f3b596ec9