Remove workaround for .qbit.api/tombstone attribute name

[d-r-q]

On Kotlin 1.3.70 tests are started to fail:

> Task :qbit-core:linuxTest
java.lang.IllegalStateException: command '/home/azhidkov/0my/Alive/qbit/repo/qbit-core/build/bin/linux/debugTest/test.kexe' exited with errors (exit code: 139)

> Task :qbit-core:runTestsWithMocha FAILED
/home/azhidkov/0my/Alive/qbit/repo/node_modules/yargs/yargs.js:1148
      else throw err
           ^

TypeError: Cannot read property 'name' of undefined
    at /home/azhidkov/0my/Alive/qbit/repo/node_modules/qbit-core.js:2290:48
    at /home/azhidkov/0my/Alive/qbit/repo/node_modules/qbit-core.js:5:5
    at Object.<anonymous> (/home/azhidkov/0my/Alive/qbit/repo/node_modules/qbit-core.js:13:2)
    at Module._compile (internal/modules/cjs/loader.js:1151:30)
    at Object.Module._extensions..js (internal/modules/cjs/loader.js:1171:10)
    at Module.load (internal/modules/cjs/loader.js:1000:32)
    at Function.Module._load (internal/modules/cjs/loader.js:899:14)
    at Module.require (internal/modules/cjs/loader.js:1040:19)
    at require (internal/modules/cjs/helpers.js:72:18)
    at /home/azhidkov/0my/Alive/qbit/repo/qbit-core/build/classes/kotlin/nodeJs/test/qbit-core_test.js:5:48
    at Object.<anonymous> (/home/azhidkov/0my/Alive/qbit/repo/qbit-core/build/classes/kotlin/nodeJs/test/qbit-core_test.js:19:2)
    at Module._compile (internal/modules/cjs/loader.js:1151:30)
    at Object.Module._extensions..js (internal/modules/cjs/loader.js:1171:10)
    at Module.load (internal/modules/cjs/loader.js:1000:32)
    at Function.Module._load (internal/modules/cjs/loader.js:899:14)
    at Module.require (internal/modules/cjs/loader.js:1040:19)
    at require (internal/modules/cjs/helpers.js:72:18)
    at /home/azhidkov/0my/Alive/qbit/repo/node_modules/mocha/lib/mocha.js:322:36
    at Array.forEach (<anonymous>)
    at Mocha.loadFiles (/home/azhidkov/0my/Alive/qbit/repo/node_modules/mocha/lib/mocha.js:319:14)
    at Mocha.run (/home/azhidkov/0my/Alive/qbit/repo/node_modules/mocha/lib/mocha.js:796:10)
    at Object.exports.singleRun (/home/azhidkov/0my/Alive/qbit/repo/node_modules/mocha/lib/cli/run-helpers.js:207:16)
    at exports.runMocha (/home/azhidkov/0my/Alive/qbit/repo/node_modules/mocha/lib/cli/run-helpers.js:300:13)
    at Object.exports.handler (/home/azhidkov/0my/Alive/qbit/repo/node_modules/mocha/lib/cli/run.js:296:3)
    at Object.runCommand (/home/azhidkov/0my/Alive/qbit/repo/node_modules/yargs/lib/command.js:238:44)
    at Object.parseArgs [as _parseArgs] (/home/azhidkov/0my/Alive/qbit/repo/node_modules/yargs/yargs.js:1072:28)
    at Object.parse (/home/azhidkov/0my/Alive/qbit/repo/node_modules/yargs/yargs.js:566:25)
    at Object.exports.main (/home/azhidkov/0my/Alive/qbit/repo/node_modules/mocha/lib/cli/cli.js:62:6)
    at Object.<anonymous> (/home/azhidkov/0my/Alive/qbit/repo/node_modules/mocha/bin/_mocha:10:23)
    at Module._compile (internal/modules/cjs/loader.js:1151:30)
    at Object.Module._extensions..js (internal/modules/cjs/loader.js:1171:10)
    at Module.load (internal/modules/cjs/loader.js:1000:32)
    at Function.Module._load (internal/modules/cjs/loader.js:899:14)
    at Function.executeUserEntryPoint [as runMain] (internal/modules/run_main.js:71:12)
    at internal/main/run_main_module.js:17:47

FAILURE: Build failed with an exception.

* What went wrong:
Execution failed for task ':qbit-core:runTestsWithMocha'.
> Process 'command 'node'' finished with non-zero exit value 1

Replace string constant with attribute, when compilers fixed. Or get rid of tombstones entirely