libprocessgroup: Use default member initializers

... instead of direct initialization in the default constructor
implementation. This allows us to just explicitly default the
constructor and provide no implementation.

Initialize class variables in the header and remove no-op constructor
to simplify code.

Bug: 346584259
Test: m
Change-Id: Iba57f5cfbf8e4d5d18ce178d39f8bcd2d76c8aaa
diff --git a/libprocessgroup/cgroup_map.h b/libprocessgroup/cgroup_map.h
index 5c6d3e2..9dd5bf5 100644
--- a/libprocessgroup/cgroup_map.h
+++ b/libprocessgroup/cgroup_map.h
@@ -32,7 +32,7 @@
   public:
     // Does not own controller
     explicit CgroupController(const ACgroupController* controller)
-        : controller_(controller), state_(UNKNOWN) {}
+        : controller_(controller) {}
 
     uint32_t version() const;
     const char* name() const;
@@ -53,7 +53,7 @@
     };
 
     const ACgroupController* controller_ = nullptr;
-    ControllerState state_;
+    ControllerState state_ = ControllerState::UNKNOWN;
 };
 
 class CgroupMap {