Changed defer checks to use explicit is True.

Using `if defer is True:` for checks instead of `if defer:` catches a
lot of weird errors that can occur if the positional args to any of the
reflected planning-method functions are shifted by one.

The previous check would return a Future if an extra argument got
passed, which concealed exceptions indicating that the arguments made
no sense, and would be passed to subsequent code until something
actually tried to query a Trajectory method on the Future.

Author: psigen

src/prpy/base/robot.py

@@ -300,7 +300,7 @@ def do_postprocess():
 
                 return CopyTrajectory(traj, env=self.GetEnv())
 
-        if defer:
+        if defer is True:
             from trollius.executor import get_default_executor
             from trollius.futures import wrap_future
 
@@ -333,7 +333,7 @@ def do_execute():
             logger.debug('Executing timed trajectory.')
             return self.ExecuteTrajectory(traj, defer=False, **kwargs)
 
-        if defer:
+        if defer is True:
             from trollius.executor import get_default_executor
             from trollius.futures import wrap_future
 
@@ -399,7 +399,7 @@ def ExecuteTrajectory(self, traj, defer=False, timeout=None, period=0.01):
                     'Trajectory includes the base, but no base controller is'
                     ' available. Is self.base.controller set?')
 
-        if defer:
+        if defer is True:
             import time
             import trollius