init/reboot: call MNT_FORCE at the last umount(2)

The last one will avoid errors=panic in ext4.

Bug: 63981945
Bug: 65481582
Change-Id: I9c86afcce441767e24fc43668ab1ff6230155a9f
Merged-In: I9c86afcce441767e24fc43668ab1ff6230155a9f
Signed-off-by: Jaegeuk Kim <jaegeuk@google.com>
(cherry picked from commit 0f04f72c2de2f5c42e62f23306bc106dddcdabb1)

init/reboot.cpp

diff --git a/init/reboot.cpp b/init/reboot.cpp
index 17e3576..5c7ddf1 100644
--- a/init/reboot.cpp
+++ b/init/reboot.cpp
@@ -84,8 +84,8 @@
           mnt_type_(entry.mnt_type),
           mnt_opts_(entry.mnt_opts) {}
 
-    bool Umount() {
-        int r = umount2(mnt_dir_.c_str(), 0);
+    bool Umount(bool force) {
+        int r = umount2(mnt_dir_.c_str(), force ? MNT_FORCE : 0);
         if (r == 0) {
             LOG(INFO) << "umounted " << mnt_fsname_ << ":" << mnt_dir_ << " opts " << mnt_opts_;
             return true;
@@ -287,11 +287,11 @@
         }
         if (emulated_devices.size() > 0 &&
             std::all_of(emulated_devices.begin(), emulated_devices.end(),
-                        [](auto& entry) { return entry.Umount(); })) {
+                        [](auto& entry) { return entry.Umount(false); })) {
             sync();
         }
         for (auto& entry : block_devices) {
-            entry.Umount();
+            entry.Umount(timeout == 0ms);
         }
         retry++;
         std::this_thread::sleep_for(100ms);