We really want f_frsize.

It's confusing, but f_bsize is not the value you're looking for; the
real block size is f_frsize.  Fix all those bugs.

Test: builds, boots
Bug: 36840579
Change-Id: I2846b8998c27f3e9a71dbf573a0a22158215a3bd
diff --git a/cmds/installd/utils.cpp b/cmds/installd/utils.cpp
index fbe6edf..943df0f 100644
--- a/cmds/installd/utils.cpp
+++ b/cmds/installd/utils.cpp
@@ -629,11 +629,10 @@
     return res;
 }
 
-int64_t data_disk_free(const std::string& data_path)
-{
+int64_t data_disk_free(const std::string& data_path) {
     struct statvfs sfs;
     if (statvfs(data_path.c_str(), &sfs) == 0) {
-        return sfs.f_bavail * sfs.f_bsize;
+        return sfs.f_bavail * sfs.f_frsize;
     } else {
         PLOG(ERROR) << "Couldn't statvfs " << data_path;
         return -1;