Automatic merge from submit-queue
Simplify a command for unmounting mounted directories
**What this PR does / why we need it**:
This PR simplifies a command for unmounting mounted directories. It replaces `cat | awk | grep` by a single `awk` expression.
**Special notes for your reviewer**:
Link about useless cat/grep usage: http://porkmail.org/era/unix/award.html#grep
**Credit**:
I saw this code fragment in the Julia Evans (@jvns) [write up](https://jvns.ca/blog/2017/07/30/a-couple-useful-ideas-from-google/).
**Release note**:
```release-note
NONE
```
CC @simo5
f37b30657e