Allow overriding /etc/fstab with $SYSTEMD_FSTAB

src/cryptsetup/cryptsetup.c

@@ -15,6 +15,7 @@
 #include "device-util.h"
 #include "escape.h"
 #include "fileio.h"
+#include "fstab-util.h"
 #include "log.h"
 #include "main-func.h"
 #include "mount-util.h"
@@ -302,7 +303,7 @@ static char *disk_mount_point(const char *label) {
         if (asprintf(&device, "/dev/mapper/%s", label) < 0)
                 return NULL;
 
-        f = setmntent("/etc/fstab", "re");
+        f = setmntent(fstab_path(), "re");
         if (!f)
                 return NULL;