use the init pid for reaper age
use the init pid for reaper age

And rename the function which returns a task's init pid.

Signed-off-by: Serge Hallyn <3df611b026e4639bee8aef7a4beb2e39fcebb313@ubuntu.com>

evgeni/pkg-lxcfs-debian,Xeno22/lxcfs,Xeno22/lxcfs,evgeni/pkg-lxcfs-debian