Logger and string usage warning fix

[SampathKumarAmex]

Description

• Removed the string concatenation from logger statement which has the placeholder
• start doesn't need to be initialised outside. IDE was showing warning for this. So, removed the variable declaration and used it inline

Motivation and Context

• Fixing a minor issue in logging (i.e. using {} and concatenation together)
• Fixed the warning on variable declaration

How Has This Been Tested?

n/a

Note:-
I can add unit test for log statement using external dependency LogCaptor. Please leave the preference in comment. I will add the below test in the separate PR. Thanks!

@Test
    public void testStringFromFileConstructorLogger() {
        LogCaptor logCaptor = LogCaptor.forClass(StringFromFile.class);
        new StringFromFile();
        assertThat(logCaptor.getDebugLogs().get(0),
                containsString("++++++++ Construct org.apache.jmeter.functions.StringFromFile@"));
    }

Screenshots (if appropriate):

Types of changes

• Bug fix (non-breaking change which fixes an issue)

Checklist:

• My code follows the code style of this project.
• I have updated the documentation accordingly.

[FSchumacher]

Thanks for the PR.

I don't think we need to check the log messages for correctness in unit tests.

[SampathKumarAmex]

I don't think we need to check the log messages for correctness in unit tests.

OK, that was proposal for the next PR.

Change 1:-

Actually, this PR addresses the unnecessary concatenation + present in the log statement.

Before change:-

log.debug("++++++++ Construct {}" + this);

After change:-

log.debug("++++++++ Construct {}", this);

Change 2:-
The second minor change is to move the String declaration to inline to fix the IDE warning.