Resolves #2779: Change FDBRecordStoreConcurrentTestBase to allow multiple paths

[ScottDugas]

This allows for having tests that involve stores at multiple different paths.

[foundationdb-ci]

Result of fdb-record-layer-pr on Linux CentOS 7

• Commit ID: affc799ee8a73922d6aa5a7d47575be85527ad90
• Duration 0:42:55
• Result: :x: FAILED
• Error: Error while executing command: ./gradlew --no-daemon --console=plain -b ./build.gradle build destructiveTest -PcoreNotStrict -PreleaseBuild=false -PpublishBuild=false -PspotbugsEnableHtmlReport. Reason: exit status 1
• Build Log terminal output (available for 30 days)
• Build Workspace zip file of the working directory (available for 30 days)

[foundationdb-ci]

Result of fdb-record-layer-pr on Linux CentOS 7

• Commit ID: 5e00ca6864c3b1a5aa79c4892bdf3e237660012a
• Duration 0:50:09
• Result: :white_check_mark: SUCCEEDED
• Error: N/A
• Build Log terminal output (available for 30 days)
• Build Workspace zip file of the working directory (available for 30 days)