Fix gitlab-rake gitlab:import:repos task

Merged Stan Hu requested to merge sh-fix-import-repos into master

Because of a change in GitLab 9.5.4 to prevent users from assuming control of a repository already on disk, the import task broke. Imports would fail with the message, "There is already a repository with that name on disk".

This change skips the validation when the import is done from the command-line.

Closes #37682 (closed)

Edited by Stan Hu