Use separate buffer in Neovim

While the behavior of 'terminal' in Vim and Neovim is different, all Neovim users cannot get backto the original buffer if terminal command has directly applied.
To make the behavior consistent, execute 'new' prior to 'terminal' in Neovim.

Author: lambdalisue

autoload/rust.vim

@@ -514,8 +514,10 @@ function! rust#Test(all, options) abort
         return rust#Run(1, '--test ' . a:options)
     endif
 
-    if has('terminal') || has('nvim')
+    if has('terminal')
         let cmd = 'terminal '
+    elseif has('nvim')
+        let cmd = 'new | terminal '
     else
         let cmd = '!'
         let manifest = shellescape(manifest)