Correctly determine repository-config lockfile path
Correctly determine repository-config lockfile path

helm repo add automatically creates a lockfile based on the repository config file path
When the given filepath did not include a file extension, a lockfile in a nonexistent directory
would have been created.

Signed-off-by: Leon Bentrup <3052d64f589b476081129ad06dcd0b283c68004a@users.noreply.github.com>
(cherry picked from commit f091b9cc01afff97d285775fb4a7cfa899ec1d4d)

helm/helm,helm/helm,bacongobbler/helm,bacongobbler/helm