Do not remove local role file if given on the commandline

using this (for testing purpose) :
  $ ansible-galaxy install COPYING
  - error: the file downloaded was not a tar.gz
  - COPYING was NOT installed successfully.
  - you can use --ignore-errors to skip failed roles.

this result in COPYING being erased, which is surprising for the user.
This also prevent erasing requirements.yml if someone use the wrong flag.
Merge pull request #8995 from mscherer/fix_galaxy

Do not remove local role file if given on the commandline