* disable pegomock --use-experimental-model-gen, cause random fail by segv
* make regen-mocks
* fix mock code which uses non experimental pegomock codes
The io/ioutil package has been deprecated as of Go 1.16, see
https://golang.org/doc/go1.16#ioutil. This commit replaces the existing
io/ioutil functions with their new definitions in io and os packages.
Signed-off-by: Eng Zer Jun <engzerjun@gmail.com>