Update TSB startup tests to use reboot.py constants

[Javier-Tan]

Description of PR

Summary:
Replace duplicated constants in test_startup_tsa_tsb_service.py to use constants already defined in reboot.py

Type of change

• Bug fix
• Testbed and Framework(new/improvement)
• Test case(new/improvement)

Back port request

• 202012
• 202205
• 202305
• 202311
• 202405

Approach

What is the motivation for this PR?

By using reboot types defined in reboot.py, increases consistency (less places to update, less potential for bugs), avoids needing to duplicate need reboot types.

How did you do it?

Import reboot.py constants into test file, replace associated values.

How did you verify/test it?

Ran affected tests on physical T2 testbed to ensure behaviour was correct

Any platform specific information?

N/A

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

N/A

Documentation

N/A

[mssonicbld]

The pre-commit check detected issues in the files touched by this pull request.
The pre-commit check is a mandatory check, please fix detected issues.

Detailed pre-commit check results:
trim trailing whitespace.................................................Passed
fix end of files.........................................................Passed
check yaml...........................................(no files to check)Skipped
check for added large files..............................................Passed
check python ast.........................................................Passed
flake8...................................................................Failed
- hook id: flake8
- exit code: 1

tests/bgp/test_startup_tsa_tsb_service.py:674:121: E501 line too long (133 > 120 characters)

flake8...............................................(no files to check)Skipped
check conditional mark sort..........................(no files to check)Skipped

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