Reland "Fix InstallServiceWorkItemTest deletes Chrome key under ClientState."

This reverts commit 9e13a828.

Reason for revert: The original CL 2086353 was not the cause of the flaky failures, so reverting the revert.

Original change's description:
> Revert "Fix InstallServiceWorkItemTest deletes Chrome key under ClientState."
> 
> This reverts commit ea173bd3.
> 
> Reason for revert: Still seeing failure of mini_installertests. Hoping this will fix the flake. Bug is https://bugs.chromium.org/p/chromium/issues/detail?id=1059314
> 
> Original change's description:
> > Fix InstallServiceWorkItemTest deletes Chrome key under ClientState.
> > 
> > Greg discovered that InstallServiceWorkItemTest.Do_ServiceName will
> > create Google\Update\ClientState\{8A69D345-D564-463c-AFF1-A69D9E530F96}
> > if it does not exist and then delete it. If the test is run on a
> > development machine, it will corrupt the stable Chrome install.
> > 
> > Bug: 1057233
> > Change-Id: I5e71c6ab9776f376dcffe0a415bfb084baec8e26
> > Reviewed-on: https://chromium-review.googlesource.com/c/chromium/src/+/2086353
> > Auto-Submit: S. Ganesh <ganesh@chromium.org>
> > Reviewed-by: Greg Thompson <grt@chromium.org>
> > Commit-Queue: Greg Thompson <grt@chromium.org>
> > Cr-Commit-Position: refs/heads/master@{#746738}
> 
> TBR=ganesh@chromium.org,grt@chromium.org
> 
> # Not skipping CQ checks because original CL landed > 1 day ago.
> 
> Bug: 1057233
> Change-Id: I57c3d50264dcf433a123e2802f04a70af8742935
> Reviewed-on: https://chromium-review.googlesource.com/c/chromium/src/+/2094466
> Reviewed-by: Scott Violet <sky@chromium.org>
> Commit-Queue: Scott Violet <sky@chromium.org>
> Cr-Commit-Position: refs/heads/master@{#748270}

TBR=sky@chromium.org,ganesh@chromium.org,grt@chromium.org

Change-Id: I561963764eae05901f083b9c235cce165e623b9d
No-Presubmit: true
No-Tree-Checks: true
No-Try: true
Bug: 1057233
Reviewed-on: https://chromium-review.googlesource.com/c/chromium/src/+/2095956Reviewed-by: S. Ganesh <ganesh@chromium.org>
Commit-Queue: S. Ganesh <ganesh@chromium.org>
Cr-Commit-Position: refs/heads/master@{#748414}

chrome/installer/util/install_service_work_item_unittest.cc

@@ -163,7 +163,7 @@ TEST_F(InstallServiceWorkItemTest, Do_ServiceName) {
           .c_str(),
       GetImpl(item.get())->GetCurrentServiceDisplayName().c_str());
 
-  EXPECT_EQ(ERROR_SUCCESS, key.DeleteKey(L""));
+  EXPECT_EQ(ERROR_SUCCESS, key.DeleteValue(kServiceName));
 }
 
 }  // namespace installer