Lazy-load LSP linters, and check b:changedtick before notifying about changes

test/lsp/test_did_save_event.vader

@@ -34,12 +34,18 @@ Before:
   \ })
   let g:ale_linters = {'foobar': ['dummy_linter']}
 
-  function! ale#linter#StartLSP(buffer, linter, callback) abort
+  function! ale#lsp_linter#StartLSP(buffer, linter, callback) abort
     let g:Callback = a:callback
 
+    let l:conn = ale#lsp#NewConnection({})
+    let l:conn.id = 347
+    let l:conn.open_documents = {a:buffer : -1}
+
     return {
+    \ 'buffer': a:buffer,
     \ 'connection_id': 347,
     \ 'project_root': '/foo/bar',
+    \ 'language_id': 'foobar',
     \}
   endfunction
 
@@ -59,6 +65,7 @@ After:
   delfunction LanguageCallback
   delfunction ProjectRootCallback
 
+  call ale#lsp#RemoveConnectionWithID(347)
   call ale#test#RestoreDirectory()
   call ale#linter#Reset()