virSetUIDGIDWithCaps: Drop redundant parenthesis around capng_apply()
After all capabilities were set (except for CAP_SETGID,
CAP_SETUID and CAP_SETPCAP) and after UID:GID was changed we drop
the last aforementioned capabilities (we couldn't drop them
before because we needed UID:GID and capabilities change).
Therefore, there's final capng_apply() call. However, it is
wrapped in one layer of parenthesis more than needed.
Signed-off-by: Michal Privoznik <mprivozn@redhat.com>