Properly handle bootstrap script in seed and lxc modules.

This is related to be605bc81a43879c15f5b026f5d2529a9b008c7e and #14865.
Rewriting the lxc module because of two concurrent implementations is not the purpose of this PR, @s0undt3ch, the purpose is to fix the bootstrap phase introduced by a CVE fix which introduced regression.
we made the decision with @thatch45 @mgwilliams a bit ago to go this way, it would be fine to stabilize it