tests: extending timeout for jsonrpc tests

Tripling timeout to lessen the probability that jsonrpc tests do not
fail on overloaded machines.

Change-Id: If7aa770282394fbf30a73a1152de88caa8b47678
Signed-off-by: pkliczewski <piotr.kliczewski@gmail.com>
Reviewed-on: http://gerrit.ovirt.org/28995
Reviewed-by: Dan Kenigsberg <danken@redhat.com>