Follow "atomic" to "group" refactoring.

Remove noisy logging about UIDs that are relying on default cache
quota of 64MiB.

Move away from yucky old statfs() and use statvfs() instead.

Test: /data/nativetest/installd_cache_test/installd_cache_test
Bug: 35812899, 35684969, 36482620
Change-Id: I3d68da97eac2ebcda489bdf9d27061cac5b3f7cc
diff --git a/cmds/installd/CacheItem.cpp b/cmds/installd/CacheItem.cpp
index 0349b0f..17eb7ff 100644
--- a/cmds/installd/CacheItem.cpp
+++ b/cmds/installd/CacheItem.cpp
@@ -38,12 +38,12 @@
 
     mParent = static_cast<CacheItem*>(p->fts_parent->fts_pointer);
     if (mParent) {
-        atomic = mParent->atomic;
+        group = mParent->group;
         tombstone = mParent->tombstone;
         mName = p->fts_name;
         mName.insert(0, "/");
     } else {
-        atomic = false;
+        group = false;
         tombstone = false;
         mName = p->fts_path;
     }