[tools] fix warning on FlagsCategory::ARRAY_SIZE

Introducing an extra utility element ARRAY_SIZE into the FlagsCategory
enumeration lead to compilation warning about unhandled enumeration value
in switch statements:

  Building CXX object src/kudu/tools/CMakeFiles/ksck.dir/ksck.cc.o
  ../../src/kudu/tools/ksck.cc: In function ‘const char* kudu::tools::FlagsCategoryToString(kudu::tools::FlagsCategory)’:
  ../../src/kudu/tools/ksck.cc:216:10: warning: enumeration value ‘ARRAY_SIZE’ not handled in switch [-Wswitch]

I think using FlagsCategory::MAX+1 instead of FlagsCategory::ARRAY_SIZE
is better than adding some special handling for ephemeral utility value
in switch statements.

This is a follow-up to a9afbce.

Change-Id: I629373583ecd010ff6e2e2a1362e5977d3ae191e
Reviewed-on: http://gerrit.cloudera.org:8080/15413
Reviewed-by: Andrew Wong <[email protected]>
Tested-by: Kudu Jenkins

src/kudu/tools/ksck-test.cc

@@ -93,7 +93,7 @@ class MockKsckMaster : public KsckMaster {
     uuid_ = uuid;
     version_ = "mock-version";
     if (is_get_flags_available_) {
-      for (size_t cat = FlagsCategory::MIN; cat < FlagsCategory::ARRAY_SIZE; ++cat) {
+      for (size_t cat = FlagsCategory::MIN; cat <= FlagsCategory::MAX; ++cat) {
         flags_by_category_[cat].flags.emplace();
       }
     }
@@ -149,7 +149,7 @@ class MockKsckTabletServer : public KsckTabletServer {
         is_get_flags_available_(is_get_flags_available) {
     version_ = "mock-version";
     if (is_get_flags_available_) {
-      for (size_t cat = FlagsCategory::MIN; cat < FlagsCategory::ARRAY_SIZE; ++cat) {
+      for (size_t cat = FlagsCategory::MIN; cat <= FlagsCategory::MAX; ++cat) {
         flags_by_category_[cat].flags.emplace();
       }
     }

src/kudu/tools/ksck.cc

@@ -191,7 +191,7 @@ std::ostream& operator<<(std::ostream& lhs, KsckFetchState state) {
 
 const FlagsFetchFilter& GetFlagsCategoryFilter(FlagsCategory category) {
   // NOTE: using double braces for std::array aggregate initialization.
-  static const std::array<FlagsFetchFilter, FlagsCategory::ARRAY_SIZE> kFilters { {
+  static const std::array<FlagsFetchFilter, FlagsCategory::MAX + 1> kFilters { {
     {
       // FlagsCategory::TIME_SOURCE
       { "time_source", "builtin_ntp_servers", },

src/kudu/tools/ksck.h

@@ -186,8 +186,7 @@ enum FlagsCategory {
   // Utility members used for range-related expressions.
   // NOTE: update the MAX member upon updates
   MIN = 0,
-  MAX = UNUSUAL,
-  ARRAY_SIZE = MAX + 1,
+  MAX = UNUSUAL
 };
 
 // Information on flags fetched using GetFlags() RPC. Consists of the status of
@@ -199,7 +198,7 @@ struct FetchedFlags {
 };
 
 // Flags retrieved using GetFlags(), indexed by FlagsCategory.
-typedef std::array<FetchedFlags, FlagsCategory::ARRAY_SIZE> FetchedFlagsByCategory;
+typedef std::array<FetchedFlags, FlagsCategory::MAX + 1> FetchedFlagsByCategory;
 
 // Structure to represent a filter to build appropriate request for GetFlags()
 // RPC.