Add container.Destroy urpc method.

This method will:
1. Stop the container process if it is still running.
2. Unmount all sanadbox-internal mounts for the container.
3. Delete the contaner root directory inside the sandbox.

Destroy is idempotent, and safe to call concurrantly.

This fixes a bug where after stopping a container, we cannot unmount the
container root directory on the host. This bug occured because the sandbox
dirent cache was holding a dirent with a host fd corresponding to a file inside
the container root on the host. The dirent cache did not know that the
container had exited, and kept the FD open, preventing us from unmounting on
the host.

Now that we unmount (and flush) all container mounts inside the sandbox, any
host FDs donated by the gofer will be closed, and we can unmount the container
root on the host.

PiperOrigin-RevId: 213737693
Change-Id: I28c0ff4cd19a08014cdd72fec5154497e92aacc9

0 files changed, 0 insertions, 0 deletions