Don't use a secdiscardable file for keys encrypted by SP

Storage keys that are encrypted by the user's synthetic password don't
need to be securely deletable by vold, since secure deletion is already
implemented at a higher level: the synthetic password protectors managed
by LockSettingsService.  Therefore, remove the use of the secdiscardable
file by vold in this case to improve performance.

Bug: 232452368
Bug: 251131631
Bug: 251147505
Change-Id: I847d6cd3b289dbeb1ca2760d6e261a78c179cad0
diff --git a/secdiscard.cpp b/secdiscard.cpp
index b91f321..490e5a1 100644
--- a/secdiscard.cpp
+++ b/secdiscard.cpp
@@ -97,7 +97,7 @@
             TEMP_FAILURE_RETRY(open(target.c_str(), O_WRONLY | O_CLOEXEC, 0)));
         if (fd == -1) {
             LOG(ERROR) << "Secure discard open failed for: " << target;
-            return 0;
+            continue;
         }
         __u32 set = 1;
         ioctl(fd, F2FS_IOC_SET_PIN_FILE, &set);