Arma 3 Image Cleanup & Refurbishment

Files:
- Remove dependency of having `libnss_wrapper.so` libraries directly in the image. Instead, use the libraries provided with their respective packages. This fixes the current 32-bit version being broken and ensures the libraries stay up to date with their respective packages.
- Slight change to passwd.template to accommodate variable name change.

Dockerfile:
- Change the base image to Debian, which from testing appears to run cleaner and faster for Arma. It also should yield a smaller image.
- Fix depreciated `ENV` call format.
- Removed un-needed packages.
- Added iproute2 package.
- Consolidated the NSS Wrapper setup to a commented group of lines to make understanding it's purpose and setup more clear.
- Added shell flag to `useradd` command.

Entrypoint:
- General cleanup.
- Changed `LD_PRELOAD`s to point to package-provided library file locations.

games/arma3/passwd.template

@@ -23,4 +23,4 @@ systemd-bus-proxy:x:103:105:systemd Bus Proxy,,,:/run/systemd:/bin/false
 syslog:x:104:108::/home/syslog:/bin/false
 messagebus:x:106:109::/var/run/dbus:/bin/false
 bind:x:108:112::/var/cache/bind:/bin/false
-${USER_NAME}:x:${USER_ID}:${GROUP_ID}:${USER_NAME}:${HOME}:/bin/bash
+${USER}:x:${USER_ID}:${GROUP_ID}:${USER}:${HOME}:/bin/bash