* fix some return types in opcodes and some types and documentation in
  parameters.
* fix serialization of the default value of the 'name' parameter in
  the opcodes related to tags when tag kind is 'cluster'
* revert changes to 'pShutdownTimeout'' and its references because the
  master branch tried to fix this inconsistency but was unable to fix
  all the references to this parameter

Signed-off-by: Jose A. Lopes <jabolopes@google.com>
Reviewed-by: Thomas Thrainer <thomasth@google.com>