python-schedutils: Correct typos in usage messages

Correct typos in usage messages
	- "chrt" should say "pchrt"
	- "taskset" should say "ptaskset"

Also update the email address for bug reports and patches.

Signed-off-by: John Kacur <jkacur@redhat.com>
Signed-off-by: Jiri Kastner <jkastner@redhat.com>