[fixes #47476347] - full bosh bootstrap re-runnable with release/stemcell already uploaded
Minor changes to bosh bootstrap in bosh aws plugin

[#47476347]
Adding a command to delete all server certificates.

[fixes #47657675]
Revert "Removing agent DNS configuration from micro bosh."

This reverts commit 80a266f888725ecd6817662c4c344a3116fb04f0.

Trying to add resolv.conf DNS resolution back so CI stemcell can resolve
DNS names.
More robust certificate uploading.

Also, updated the external spec to use the generated domain name from the BOSH
environment variables.