test: isolate completion server state

Author: georgewfraser

src/test/java/org/javacs/CompletionsBase.java

@@ -5,10 +5,16 @@
 import java.util.stream.Stream;
 import org.javacs.lsp.*;
 import org.junit.Assert;
+import org.junit.Before;
 
 public class CompletionsBase {
     protected static JavaLanguageServer server = LanguageServerFixture.getJavaLanguageServer();
 
+    @Before
+    public void resetServer() {
+        refreshServer();
+    }
+
     protected void refreshServer() {
         server = LanguageServerFixture.getJavaLanguageServer();
     }