It has been observed that some chroot operations spawn additional
processes which rely on chroot files. More specifically, zypper, uses
gpg-agent to import and validate gpg keys for its repositories. This
gpg-agent process may stay alive for longer which prevents unmounting of
the tmpfs directory since the gpg-agent process still uses libraries etc
which were present in the chroot. We try to solve this by using walking
all the pids in /proc to find out the running processes in the chroot and
kill them gracefully. If that fails for whatever reason, then we simply
keep trying to umount the tmpfs directory before we give up.
The gpg-agent process usually terminates soon after its home directory
disappears but on fast systems we can reach the 'umount tmpfs' point
before gpg-agent terminates by itself. The solution is generic enough so
other 'chroot processes' can also be handled appropriately.
Change-Id: Iccf332678c79266113e76f062884fc5ee79e515d