Ensure project and pom.xml diagnostics are properly reset

[fbricon]

Fixes #814

[snjeza]

@fbricon WorkspaceDiagnosticsHandlerTest.testMissingNatures() fails

diff --git a/org.eclipse.jdt.ls.tests/src/org/eclipse/jdt/ls/core/internal/handlers/WorkspaceDiagnosticsHandlerTest.java b/org.eclipse.jdt.ls.tests/src/org/eclipse/jdt/ls/core/internal/handlers/WorkspaceDiagnosticsHandlerTest.java
index 741025d8..9d2d68e9 100644
--- a/org.eclipse.jdt.ls.tests/src/org/eclipse/jdt/ls/core/internal/handlers/WorkspaceDiagnosticsHandlerTest.java
+++ b/org.eclipse.jdt.ls.tests/src/org/eclipse/jdt/ls/core/internal/handlers/WorkspaceDiagnosticsHandlerTest.java
@@ -11,7 +11,6 @@
 package org.eclipse.jdt.ls.core.internal.handlers;
 
 import static org.junit.Assert.assertEquals;
-import static org.junit.Assert.assertFalse;
 import static org.junit.Assert.assertTrue;
 import static org.mockito.Mockito.atLeastOnce;
 import static org.mockito.Mockito.mock;
@@ -251,7 +250,7 @@ public class WorkspaceDiagnosticsHandlerTest extends AbstractProjectsManagerBase
                Collections.reverse(allCalls);
                projectsManager.setConnection(client);
                Optional<PublishDiagnosticsParams> projectDiags = allCalls.stream().filter(p -> p.getUri().endsWith("eclipse/wtpproject")).findFirst();
-               assertFalse(projectDiags.isPresent());
+               assertTrue(projectDiags.get().getDiagnostics().isEmpty());
        }
 
        @Test

[fbricon]

test this please

[fbricon]

@snjeza added tests