Tries to cancel a task.
See also
Other task functions:
opal.task(),
opal.task_wait(),
opal.tasks()
Examples
if (FALSE) { # \dontrun{
o <- opal.login('administrator','password', url='https://opal-demo.obiba.org')
opal.task_cancel(o, '1')
opal.logout(o)
} # }