[Nearby] Clear active profile in teardown to fix unit-tests

The active profile was not being cleared on the |NearbyProcessManager|
singleton in the unit-test tear down which was causing unit-test
failures.

Change-Id: Iefe1b037beeb23924550c9ae6ccaf1ba0f111b5f
Reviewed-on: https://chromium-review.googlesource.com/c/chromium/src/+/2354616
Commit-Queue: James Vecore <vecore@google.com>
Commit-Queue: Ryan Hansberry <hansberry@chromium.org>
Auto-Submit: James Vecore <vecore@google.com>
Reviewed-by: Ryan Hansberry <hansberry@chromium.org>
Cr-Commit-Position: refs/heads/master@{#797774}

chrome/browser/nearby_sharing/nearby_sharing_service_impl_unittest.cc

@@ -252,7 +252,10 @@ class NearbySharingServiceImplTest : public testing::Test {
         .WillRepeatedly(testing::Return(&mock_decoder_));
   }
 
-  void TearDown() override { profile_manager_.DeleteAllTestingProfiles(); }
+  void TearDown() override {
+    profile_manager_.DeleteAllTestingProfiles();
+    NearbyProcessManager::GetInstance().ClearActiveProfile();
+  }
 
   std::unique_ptr<NearbySharingServiceImpl> CreateService(
       const std::string& profile_name) {