Set groups before dropping privileges.

The code for dumping tombstones tries to read the log data. This was
silently failing after the change to drop root privileges. Fix this
by explicitly setting the groups allowed before dropping privileges.

Bug: 28590884
(cherry picked from commit edc23801091f1a909efe130e0dba8abab3329eb5)

Change-Id: I225365edccb11f8752027566fd42f3b10ce10260
1 file changed