Wrap flock with TEMP_FAILURE_RETRY.

flock may return EINTR. There are code using LockShared() to test
existance of the directory. Don't fail spuriously.

Test: pass
Bug: 160457903
Change-Id: I51628abe05599422eb3f344781d8f3acd653c822
diff --git a/fs_mgr/libsnapshot/snapshot.cpp b/fs_mgr/libsnapshot/snapshot.cpp
index a287c35..4178349 100644
--- a/fs_mgr/libsnapshot/snapshot.cpp
+++ b/fs_mgr/libsnapshot/snapshot.cpp
@@ -1846,7 +1846,7 @@
         PLOG(ERROR) << "Open failed: " << file;
         return nullptr;
     }
-    if (lock_flags != 0 && flock(fd, lock_flags) < 0) {
+    if (lock_flags != 0 && TEMP_FAILURE_RETRY(flock(fd, lock_flags)) < 0) {
         PLOG(ERROR) << "Acquire flock failed: " << file;
         return nullptr;
     }
@@ -1857,7 +1857,7 @@
 }
 
 SnapshotManager::LockedFile::~LockedFile() {
-    if (flock(fd_, LOCK_UN) < 0) {
+    if (TEMP_FAILURE_RETRY(flock(fd_, LOCK_UN)) < 0) {
         PLOG(ERROR) << "Failed to unlock file: " << path_;
     }
 }