Don't spawn uprobes tests with sudo

Don't spawn uprobes tests with sudo

Using spawn with sudo doesn't work well, because the password prompt
won't go to the correct TTY.  The only reason that the uprobes tests
needed to do this is so uprobes.ko could be built as root.  Now instead,
I've added a pre-check that will directly call the uprobes make with
sudo (via the as_root proc).

* testsuite/lib/systemtap.exp (uprobes_p): Check and build uprobes.ko.
* testsuite/systemtap.base/uprobes.exp: Use uprobes_p; don't spawn sudo.
* testsuite/systemtap.base/bz6850.exp: Ditto.
* testsuite/systemtap.base/bz10078.exp: Ditto.
* testsuite/systemtap.base/bz6905.exp: sudo isn't needed for -p2.