generate csv: do not generate a package manifest for bundles

[estroz]

Description of the change:

• cmd/operator-sdk/generate: skip package manifest generation if --make-manifests=true (the default)

Motivation for the change: package manifests are not part of bundles

/kind bug

[estroz]

/cherry-pick v0.17.x

[openshift-cherrypick-robot]

@estroz: #3014 failed to apply on top of branch "v0.17.x":

error: Failed to merge in the changes.
Using index info to reconstruct a base tree...
M	cmd/operator-sdk/generate/csv.go
Falling back to patching base and 3-way merge...
Auto-merging cmd/operator-sdk/generate/csv.go
CONFLICT (content): Merge conflict in cmd/operator-sdk/generate/csv.go
Patch failed at 0001 generate csv: do not generate a package manifest when --make-manifests=true

In response to this:

/cherry-pick v0.17.x

Instructions for interacting with me using PR comments are available here. If you have questions or suggestions related to my behavior, please file an issue against the kubernetes/test-infra repository.