Commit 05513284e7 exposed the "rootfs"
and "no-pivot" flags for the "containers" command, but it accidentally
removed them for "run" since package-level variables are initialized
before package-level init functions in golang. Hoisting these flags to
a package imported by both commands solves the problem.
Signed-off-by: Felix Abecassis <fabecassis@nvidia.com>