Add --no-unlink option to secdiscard for testing.

Also allow deletion of multiple files in one invocation.

Change-Id: I5011bf45f2d3b91964bc68fd8e61ec037e1de2ca
diff --git a/Ext4Crypt.cpp b/Ext4Crypt.cpp
index c337dbb..c8415d6 100644
--- a/Ext4Crypt.cpp
+++ b/Ext4Crypt.cpp
@@ -660,6 +660,7 @@
         SLOGD("Forked for secdiscard");
         execl("/system/bin/secdiscard",
             "/system/bin/secdiscard",
+            "--",
             key_path.c_str(),
             NULL);
         SLOGE("Unable to launch secdiscard on %s: %s\n", key_path.c_str(),