Removed duplicate vagrant complation

The vagrant.plugin.bash file only defined a completion function, nothing
more. The vagrant.completion.bash file has a more recent completion
function for vagrant. We don't need both, and the completion in the
plugin file was in the wrong location in the first place.

plugins/available/vagrant.plugin.bash

@@ -1,52 +0,0 @@
-cite about-plugin
-about-plugin 'set up vagrant autocompletion'
-
-_vagrant()
-{
-    cur="${COMP_WORDS[COMP_CWORD]}"
-    prev="${COMP_WORDS[COMP_CWORD-1]}"
-    commands="box destroy halt help init package provision reload resume ssh ssh_config status suspend up version"
-
-    if [ $COMP_CWORD == 1 ]
-    then
-      COMPREPLY=($(compgen -W "${commands}" -- ${cur}))
-      return 0
-    fi
-
-    if [ $COMP_CWORD == 2 ]
-    then
-        case "$prev" in
-            "box")
-              box_commands="add help list remove repackage"
-              COMPREPLY=($(compgen -W "${box_commands}" -- ${cur}))
-              return 0
-            ;;
-            "help")
-              COMPREPLY=($(compgen -W "${commands}" -- ${cur}))
-              return 0
-            ;;
-            *)
-            ;;
-        esac
-    fi
-
-    if [ $COMP_CWORD == 3 ]
-    then
-      action="${COMP_WORDS[COMP_CWORD-2]}"
-      if [ $action == 'box' ]
-      then
-        case "$prev" in
-            "remove"|"repackage")
-              local box_list=$(find $HOME/.vagrant/boxes/* -maxdepth 0 -type d -printf '%f ')
-              COMPREPLY=($(compgen -W "${box_list}" -- ${cur}))
-              return 0
-              ;;
-            *)
-            ;;
-        esac
-      fi
-    fi
-
-}
-complete -F _vagrant vagrant
-