fix: ensure correct run context for 'cassandra-driver' instrumentation

[trentm]

Refs: #2430

Checklist

• Implement code
• Add tests
• Update documentation
• Add CHANGELOG.asciidoc entry
• Commit message follows commit guidelines

[trentm]

The parent-child relationships from a run of examples/trace-cassandra-driver.js, before the run context fixes here:

    trace f40047
    `- transaction 7be43a "t1" (265.315ms, outcome=unknown)
       `- span 2d0073 "Cassandra: Connect" (41.431ms)
         `- span f24f13 "SELECT FROM system.local" (5.716ms)
           `- span ea5145 "CREATE" (1.807ms)
             `- span 8a1b0f "CREATE TABLE IF" (58.492ms)
               `- span 6c6f4c "Cassandra: Batch query" (36.157ms)
                 `- span a940e2 "Cassandra: Connect" (32.173ms)
                   `- span 1902a4 "SELECT FROM testtable" (3.387ms)
                     `- span 8679a9 "SELECT FROM testtable" (5.291ms)
                       `- span 296225 "DROP TABLE testtable" (99.723ms)

and after:

    trace 510b5e
    `- transaction 486ec1 "t1" (296.725ms, outcome=unknown)
       `- span d0d033 "Cassandra: Connect" (45.644ms)
       `- span 9d0350 "SELECT FROM system.local" (5.321ms)
       `- span 16ba1c "CREATE" (23.662ms)
       `- span 408cfd "CREATE TABLE IF" (44.923ms)
       `- span cb0d75 "Cassandra: Batch query" (36.014ms)
       `- span 8a037a "Cassandra: Connect" (31.812ms)
       `- span a1dfa7 "SELECT FROM testtable" (3.676ms)
       `- span 8b5d32 "SELECT FROM testtable" (3.573ms)
       `- span 7f117d "DROP TABLE testtable" (120.867ms)

[apmmachine]

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• Reason: null

• Start Time: 2022-01-26T21:08:30.133+0000

• Duration: 51 min 38 sec

• Commit: dd3ace1

Test stats 🧪

Test	Results
Failed	0
Passed	243225
Skipped	0
Total	243225

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[trentm]

run module tests for cassandra-driver