Fix labelfloat properties

When building the presentation slides with version 2.36 of Graphviz,
the graphs that do not specify the labelfloat=true fully fail to build.
Using dot -T png rebase.txt -o rebase.html would show an error:

  Warning: rebase.txt: syntax error in line X near ']'

Change-Id: I7a4847e53ee57709042a62c24fe8f20c7544a912