fix(mocks): always call functions injected with inject with this set to the current spec

Currently when a function is injected inside of a test we set the context to undefined which
is a bug.

Closes angular#6102

Author: wesalvaro

src/ngMock/angular-mocks.js

@@ -2125,7 +2125,7 @@ if(window.jasmine || window.mocha) {
   window.inject = angular.mock.inject = function() {
     var blockFns = Array.prototype.slice.call(arguments, 0);
     var errorForStack = new Error('Declaration Location');
-    return isSpecRunning() ? workFn() : workFn;
+    return isSpecRunning() ? workFn.call(currentSpec) : workFn;
     /////////////////////
     function workFn() {
       var modules = currentSpec.$modules || [];

test/ngMock/angular-mocksSpec.js

@@ -864,6 +864,25 @@ describe('ngMock', function() {
       });
 
 
+      describe('this', function() {
+
+        it('should set `this` to be the jasmine context', inject(function() {
+          expect(this instanceof jasmine.Spec).toBe(true);
+        }));
+
+        it('should set `this` to be the jasmine context when inlined in a test', function() {
+          var tested = false;
+
+          inject(function() {
+            expect(this instanceof jasmine.Spec).toBe(true);
+            tested = true;
+          });
+
+          expect(tested).toBe(true);
+        });
+      });
+
+
       // We don't run the following tests on IE8.
       // IE8 throws "Object does not support this property or method." error,
       // when thrown from a function defined on window (which `inject` is).