Make TracingDataSource implements AutoCloseable

[quaff]

Container like spring ApplicationContext will close underlying DataSource automatically.

    @Bean
    public DataSource dataSource() {
        DataSource ds = createDataSource();
        if (tracingEnabled) {
            ds = new TracingDataSource(tracingConfiguration.getTracer(), ds);
            //the underlying ds will not be closed since it's not managed by spring now
        }
        return ds;
    }

[coveralls]

Pull Request Test Coverage Report for Build 257

• 0 of 3 (0.0%) changed or added relevant lines in 1 file are covered.
• No unchanged relevant lines lost coverage.
• Overall coverage decreased (-0.1%) to 47.804%

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Changes Missing Coverage	Covered Lines	Changed/Added Lines	%
src/main/java/io/opentracing/contrib/jdbc/TracingDataSource.java	0	3	0.0%
<!--	Total:	0	3	0.0%	-->

Totals
Change from base Build 253:	-0.1%
Covered Lines:	468
Relevant Lines:	979

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💛 - Coveralls