perf/vhost: Add nullglob,extglob opts

Previously conf-generator did depend on these being set by the
scheduler/common.sh, but since the:

https://review.spdk.io/gerrit/c/spdk/spdk/+/19551



these were moved to autotest_common.sh. conf-generator is not
meant to use it, so enable these opts directly inside of it.

Change-Id: I00a70250e2b240e27345a344848deb0fc406209e
Signed-off-by: Michal Berger <michal.berger@intel.com>
Reviewed-on: https://review.spdk.io/gerrit/c/spdk/spdk/+/20581


Reviewed-by: Konrad Sztyber <konrad.sztyber@intel.com>
Reviewed-by: Tomasz Zawadzki <tomasz.zawadzki@intel.com>
Tested-by: SPDK CI Jenkins <sys_sgci@intel.com>