Fix alluxio-fuse unmount to get the right pid when no options
Fix alluxio-fuse unmount to get the right pid when no options

### What changes are proposed in this pull request?

Fix alluxio-fuse unmount to get the right pid when no options provided
during mounting.

### Why are the changes needed?

I submitted a PR [Fix alluxio-fuse unmount to get the right
pid](https://github.com/Alluxio/alluxio/pull/15897) about two months
ago. For that PR, I was always testing with setting mount options. For
example, `-o default_permissions`.

Now I found that (with options)/(without options) made the matching
pattern have different indexes, and the solution is to make the pattern
has consistent indexes.

### Does this PR introduce any user facing changes?

No

pr-link: Alluxio/alluxio#16179
change-id: cid-ca5f442e3d1c634260194e7c7648410d66afc467
wwjiang007/alluxio,wwjiang007/alluxio,wwjiang007/alluxio,Alluxio/alluxio,Alluxio/alluxio,wwjiang007/alluxio,Alluxio/alluxio,Alluxio/alluxio,Alluxio/alluxio,wwjiang007/alluxio,wwjiang007/alluxio,wwjiang007/alluxio,Alluxio/alluxio,Alluxio/alluxio,Alluxio/alluxio,wwjiang007/alluxio,Alluxio/alluxio,wwjiang007/alluxio,Alluxio/alluxio,wwjiang007/alluxio