update_engine: fixed remaining linter and some spelling errors

Fixed remaining errors from cpplint as well as some spelling errors
mostly in comments.

BUG=None
TEST=FEATURES=test emerge-link update_engine

Change-Id: I484988ab846ac5a3c68c016ddccfb247f225ec27
Reviewed-on: https://chromium-review.googlesource.com/208897
Reviewed-by: Alex Vakulenko <avakulenko@chromium.org>
Commit-Queue: Alex Vakulenko <avakulenko@chromium.org>
Tested-by: Alex Vakulenko <avakulenko@chromium.org>
diff --git a/hardware.cc b/hardware.cc
index 0ffd58f..a83d1b3 100644
--- a/hardware.cc
+++ b/hardware.cc
@@ -85,7 +85,7 @@
 
   std::string disk_name = utils::GetDiskName(Hardware::BootKernelDevice());
   if (disk_name.empty()) {
-    LOG(ERROR) << "Failed to get the cuurent kernel boot disk name";
+    LOG(ERROR) << "Failed to get the current kernel boot disk name";
     return std::vector<std::string>();
   }