Close partially opened guest session when IGuest.create_session() fails

[busan15]

Ensures that guest sessions created with IGuest.create_session() are properly closed in case of failure. Closes #101.

[busan15]

Through further testing it appears that the default value of timeout_ms=0 can sometimes get the process to hang indefinitely while waiting for a failed session to finish terminating. Setting a fixed timeout of 5 seconds should be enough to give the session a chance to terminate properly while not blocking the rest of the program for too long.