libprocessgroup: add flags to indicate when a controller failed to mount

Controllers listed in cgroups.json file might fail to mount if kernel is
not configured to support them. We need a way to indicate whether a
controller was successfully mounted and is usable to avoid logging errors
and warnings when a controller that failed to mount is being used. Add
flags bitmask to cgrouprc controller descriptor and use a bit to indicate
that controller is successfully mounted. Modify cpusets_enabled() and
schedboost_enabled() functions to use this bit and report the actual
availability of the controller.

Bug: 124080437
Test: libcutils_test with cpuset and schedtune controllers disabled
Change-Id: I770cc39fe50465146e3205aacf77dc3c56923c5d
Signed-off-by: Suren Baghdasaryan <surenb@google.com>
diff --git a/libprocessgroup/sched_policy.cpp b/libprocessgroup/sched_policy.cpp
index fe4f93b..15f8139 100644
--- a/libprocessgroup/sched_policy.cpp
+++ b/libprocessgroup/sched_policy.cpp
@@ -151,19 +151,19 @@
 }
 
 bool cpusets_enabled() {
-    static bool enabled = (CgroupMap::GetInstance().FindController("cpuset").HasValue());
+    static bool enabled = (CgroupMap::GetInstance().FindController("cpuset").IsUsable());
     return enabled;
 }
 
 bool schedboost_enabled() {
-    static bool enabled = (CgroupMap::GetInstance().FindController("schedtune").HasValue());
+    static bool enabled = (CgroupMap::GetInstance().FindController("schedtune").IsUsable());
     return enabled;
 }
 
 static int getCGroupSubsys(int tid, const char* subsys, std::string& subgroup) {
     auto controller = CgroupMap::GetInstance().FindController(subsys);
 
-    if (!controller.HasValue()) return -1;
+    if (!controller.IsUsable()) return -1;
 
     if (!controller.GetTaskGroup(tid, &subgroup)) {
         LOG(ERROR) << "Failed to find cgroup for tid " << tid;