fix issue with sys.path. 

Now the path looks like ['root/gluon', 'root/site-packages', 'root'] like in a normal web request. Given that the recommended way to start the scheduler on its own is to do 
     
     python gluon/scheduler.py -u .....

there are no problems with the sys.path at all: the sys.path dance is not needed and we're back having exactly the same sys.path as every other web request/shell environment . Discussion on the sys.path dance has been done here https://github.com/web2py/web2py/pull/156

Hope it's the final one.
Thanks again to @jklundell for reviewing and the patience.