Add unittest for PycURL 7.19.0's reset issue

While we won't use this function in Ganeti (yet), users should be aware
of the potential crashes caused by this functioni (discussed offline).
If the installed version of PycURL is not affected, this test is a
no-op.

Signed-off-by: Michael Hanselmann <hansmi@google.com>
Reviewed-by: Guido Trotter <ultrotter@google.com>