MacOSX: Fix run_all_unittests target name conflict

There is a target name conflict between packager/base/base.gyp:run_all_unittests and
media_test.gyp:run_all_unittests. Change to media_test.gyp:run_tests_with_atexit_manager to
resolve the conflict.

packager/media/event/media_event.gyp

@@ -46,7 +46,7 @@
         '../../testing/gtest.gyp:gtest',
         # Depends on full protobuf to read/write with TextFormat.
         '../../third_party/protobuf/protobuf.gyp:protobuf_full_do_not_use',
-        '../test/media_test.gyp:run_all_unittests',
+        '../test/media_test.gyp:run_tests_with_atexit_manager',
         'media_event',
       ],
     },

packager/media/file/file.gyp

@@ -54,7 +54,7 @@
       'dependencies': [
         '../../testing/gtest.gyp:gtest',
         '../../third_party/gflags/gflags.gyp:gflags',
-        '../test/media_test.gyp:run_all_unittests',
+        '../test/media_test.gyp:run_tests_with_atexit_manager',
         'file',
       ],
     },

packager/media/test/media_test.gyp

@@ -10,7 +10,7 @@
   ],
   'targets': [
     {
-      'target_name': 'run_all_unittests',
+      'target_name': 'run_tests_with_atexit_manager',
       'type': '<(component)',
       'sources': [
         'run_tests_with_atexit_manager.cc',
@@ -28,7 +28,7 @@
       ],
       'dependencies': [
         '../../base/base.gyp:base',
-        'run_all_unittests',
+        'run_tests_with_atexit_manager',
       ],
     },
   ],

packager/mpd/mpd.gyp

@@ -100,7 +100,7 @@
       'dependencies': [
         '../base/base.gyp:base',
         '../media/file/file.gyp:file',
-        '../media/test/media_test.gyp:run_all_unittests',
+        '../media/test/media_test.gyp:run_tests_with_atexit_manager',
         '../testing/gmock.gyp:gmock',
         '../testing/gtest.gyp:gtest',
         'mpd_builder',