yamllint: fix all yamllint colons, commas and empty-lines errors

Fix all colons and commas errors detected by yamllint:

yamllint -f parsable -c .yamllint $( find -regex '.*\.y[a]*ml' ) | \
  grep '(brackets)'

yamllint -f parsable -c .yamllint $( find -regex '.*\.y[a]*ml' ) | \
  grep '(commas)'

yamllint -f parsable -c .yamllint $( find -regex '.*\.y[a]*ml' ) | \
  grep '(empty-lines)'

Default config is no space before, one space after, max 2 empty lines.

Signed-off-by: Fabio Baltieri <fabiobaltieri@google.com>