Make trailing slash in scale_install_repository_url optional

[acch]

According to the documentation, scale_install_repository_url should contain a trailing slash:

# Remember the trailing slash `/` in the URL
- scale_install_repository_url: http://server/path/

This is because some (not all!) of the code contains the following syntax (which would break if the variable doesn't end with a slash /):

# example: roles/core/node/tasks/install_repository.yml:
baseurl: "{{ scale_install_repository_url }}gpfs_rpms/"

The above syntax can be found in the following files:

• roles/core/node/tasks/install_repository.yml
• roles/nfs/node/tasks/install_repository.yml
• roles/smb/node/tasks/install_repository.yml
• roles/callhome/node/tasks/install_repository.yml
• roles/scale_fileauditlogging/node/tasks/install_repository.yml
• roles/zimon/node/tasks/install_repository.yml

Note that the following file contains the correct syntax already:

# roles/gui/node/tasks/install_repository.yml:
baseurl: "{{ scale_install_repository_url }}/gpfs_rpms/"

This syntax is more robust as with more than one slash / the path would still be valid, and this would make the trailing slash / optional...