Use same naming scheme like bash-completion

[robert-scheck]

As of writing, all bash-completion files installed by IcedTea-Web are named e.g. /usr/share/bash-completion/completions/javaws.bash while bash-completion itself uses a naming scheme without .bash, thus e.g. /usr/share/bash-completion/completions/javaws would conform upstream's naming scheme.

Example file lists from downstreams packaging bash-completion:

• Fedora: https://packages.fedoraproject.org/pkgs/bash-completion/bash-completion/fedora-rawhide.html#files
• Debian: https://packages.debian.org/sid/all/bash-completion/filelist