The check is to gate removing a line in known_hosts file, so the check
needs to be checking /root/.ssh/known_hosts.

Signed-off-by: Ying Xie <ying.xie@microsoft.com>

…ew test on th5 (sonic-net#1018)

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### Description of PR
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Summary:
Fixes # (issue)

### Type of change

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- Fill x for your type of change.
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- [x] Bug fix
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- [ ] Bug fix
- [ ] Testbed and Framework(new/improvement)
- [ ] New Test case
 - [ ] Skipped for non-supported platforms
- [ ] Test case improvement

### Back port request
- [ ] 202205
- [ ] 202305
- [ ] 202311
- [ ] 202405
- [ ] 202411
- [x] 202412
- [ ] 202505
- [x] 202511

### Approach
#### What is the motivation for this PR?
In the last portion of the trimming counters test, all buffer profiles have trimming turned off. The test expects the trimming counters to stay the same after this happens. This fails on th5 because the Broadcom SAI clears counters when the trimming feature has been turned off. Microsoft has requested that Broadcom change the SAI implementation, but until that happens we need to ensure this issue doesn't affect the pass rate.

#### How did you do it?
Split the problematic portion of the test into it's own testcase. We will be skipping this new testcase on th5 until the SAI implementation is changed to support the expected behavior.

#### How did you verify/test it?
Tested internally, verifying the new testcase was skipped and the existing testcase was not failing with the previously described issue.

#### Any platform specific information?
We are only skipping for th5, other vendors may need to add to the skip condition if they have the same issue.

#### Supported testbed topology if it's a new test case?

### Documentation
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Fix error when running 'show lldp table' or 'show lldp neighbor'
through SSH command. (sonic-net#1067)
[201911]: Multi asic show interface support (sonic-net#1070)
[counterpoll] Add new FC group for port buffer drop counters
(sonic-net#1024)
[201911] show interface portchannel support for Multi ASIC
(sonic-net#1071)
Fix a typo in mellanox_buffer_migrator (sonic-net#1090)
Fix pfcwd stats crash with invalid queue name (sonic-net#1077)
[PFCWD] Fix issue with "pfcwd show stats" command during SONiC init
(sonic-net#1018)
enable watchdog before running platform specific reboot plugin
(sonic-net#1037)
Add namespace of the process in the coredump filename. (sonic-net#1091)