Only pass nomblk_io_submit option when mounting ext4

This option only exists for ext4 filesystems, so it shouldn't be
used when mounting ext2/ext3.
This bug would cause the mount system call in check_fs to always fail
with ext2/ext3 filesystems.

Change-Id: I3c8938029357a4a4170355118b6757f61ff4b227
diff --git a/fs_mgr/fs_mgr.c b/fs_mgr/fs_mgr.c
index bb2bed2..42f25c7 100644
--- a/fs_mgr/fs_mgr.c
+++ b/fs_mgr/fs_mgr.c
@@ -95,7 +95,7 @@
     int status;
     int ret;
     long tmpmnt_flags = MS_NOATIME | MS_NOEXEC | MS_NOSUID;
-    char *tmpmnt_opts = "nomblk_io_submit,errors=remount-ro";
+    char tmpmnt_opts[64] = "errors=remount-ro";
     char *e2fsck_argv[] = {
         E2FSCK_BIN,
         "-y",
@@ -118,6 +118,10 @@
          * fix the filesystem.
          */
         errno = 0;
+        if (!strcmp(fs_type, "ext4")) {
+            // This option is only valid with ext4
+            strlcat(tmpmnt_opts, ",nomblk_io_submit", sizeof(tmpmnt_opts));
+        }
         ret = mount(blk_device, target, fs_type, tmpmnt_flags, tmpmnt_opts);
         INFO("%s(): mount(%s,%s,%s)=%d: %s\n",
              __func__, blk_device, target, fs_type, ret, strerror(errno));