fixed bug where esp_vfs_unregister would unregister root file system

[ThomasRogg]

when it should unregister sub-filesystem (such as /sdcard)
path comparison must be exact here

[CLAassistant]

Thank you for your submission, we really appreciate it. Like many open source projects, we ask that you sign our Contributor License Agreement before we can accept your contribution.
_{You have signed the CLA already but the status is still pending? Let us recheck it.}

[ThomasRogg]

Won't sign license agreement, not worth the hassle for me.
This is a clear bug. I would suggest you fix this.

[igrr]

Thanks for finding the bug and submitting the PR, @neoniousTR! Since you have not signed the CLA, we'll treat this as an issue report. Will keep this open until respective fix is merged.

[ThomasRogg]

You're welcome.

[fivdi]

Won't sign license agreement, not worth the hassle for me.

@neoniousTR I'm not sure if you are aware of this but signing the license agreement should actually be easy and if I'm not mistaken it can be done with your GitHub account. Just click on the "CLA | not signed yet" badge in the above post and follow the instructions.