fix ManTest

Signed-off-by: Mabel Zhang <mabel@openrobotics.org>

Author: mabelzhang

gazebo/gazebo.1.ronn

@@ -49,6 +49,8 @@ Gazebo server runs simulation and handles commandline options, starts a Master,
  Load a server plugin.
 * -o, --profile arg :
  Physics preset profile name from the options in the world file.
+* --lockstep :
+ Lockstep simulation so sensor update rates are respected.
 
 
 ## AUTHOR

gazebo/gzserver.1.ronn

@@ -19,6 +19,8 @@ Gazebo server runs simulation and handles commandline options, starts a Master,
  Produce this help message.
 * -u, --pause :
  Start the server in a paused state.
+* --lockstep :
+ Lockstep simulation so sensor update rates are respected.
 * -e, --physics arg :
  Specify a physics engine (ode|bullet|dart|simbody).
 * -p, --play arg :