shutil.which is not always use for dynamips path and not correctly used for iouyap

[julien-duponchelle]

e481ffa#commitcomment-18803303

[ghost]

ubridge_path and vpcs_path are behaving the same as iouyap_path, so all xxx_path variables should be changed.

[julien-duponchelle]

A little note about shutil.which if the path doesn't exists which return None preventing you to use the path later in a error message.

I will workaround that

[julien-duponchelle]

Should be OK now thanks for the idea