Fix CVE-2016-1531

Fix CVE-2016-1531

Add keep_environment, add_environment.
Change the working directory to "/" during the early startup
phase.

(cherry picked from commit bc3c7bb7d4aba3e563434e5627fe1f2176aa18c0)
    (cherry picked from commit 2b92b67bfc33efe05e6ff2ea3852731ac2273832)
    (cherry picked from commit 14b82c8b736c8ed24eda144f57703cb9feac6323)
    (cherry picked from commit 9ca92d0c6e9c6f161bd8111366c6952d3a9315e2)
    (cherry picked from commit 0020c6d9ecfd98ed7b2b337ed4f898fdc409784b)
    (cherry picked from commit e8f96966360ea8867ad6a8b5affda6c37fa4958c)
    (cherry picked from commit ef6fb807c1e1a665f444f644c60c77269f7c5209)