[crystal] Fix some issues in crystal client templates

Created by: cyangle

@wing328 Fixed some issues found when using crystal generator to generate client library for google drive v3 api tests failed with below errors:

366313 [ERROR] Failed to execute goal org.apache.maven.plugins:maven-surefire-plugin:3.0.0-M5:test (default-test) on project openapi-generator: There are test failures.
366313 [ERROR] 
366313 [ERROR] Please refer to /gen/modules/openapi-generator/target/surefire-reports for the individual test results.
366313 [ERROR] Please refer to dump files (if any exist) [date].dump, [date]-jvmRun[N].dump and [date].dumpstream.
366313 [ERROR] ExecutionException The forked VM terminated without properly saying goodbye. VM crash or System.exit called?
366313 [ERROR] Command was /bin/sh -c cd /gen/modules/openapi-generator && /usr/local/openjdk-8/jre/bin/java -Xmx1024m -XX:MaxPermSize=256m org.apache.maven.surefire.booter.ForkedBooter /gen/modules/openapi-generator/target/surefire 2021-10-19T04-17-42_620-jvmRun1 surefire1215040486184154595tmp surefire_32415854988303674911tmp
366313 [ERROR] Error occurred in starting fork, check output in log
366314 [ERROR] Process Exit Code: 137
366314 [ERROR] Crashed tests:
366314 [ERROR] org.openapitools.codegen.kotlin.spring.KotlinSpringServerCodegenTest
366314 [ERROR] org.apache.maven.surefire.booter.SurefireBooterForkException: ExecutionException The forked VM terminated without properly saying goodbye. VM crash or System.exit called?
366314 [ERROR] Command was /bin/sh -c cd /gen/modules/openapi-generator && /usr/local/openjdk-8/jre/bin/java -Xmx1024m -XX:MaxPermSize=256m org.apache.maven.surefire.booter.ForkedBooter /gen/modules/openapi-generator/target/surefire 2021-10-19T04-17-42_620-jvmRun1 surefire1215040486184154595tmp surefire_32415854988303674911tmp

PR checklist

• Read the contribution guidelines.
• Pull Request title clearly describes the work in the pull request and Pull Request description provides details about how to validate the work. Missing information here may result in delayed response from the community.
• Run the following to build the project and update samples:

  ./mvnw clean package 
  ./bin/generate-samples.sh
  ./bin/utils/export_docs_generators.sh

  Commit all changed files. This is important, as CI jobs will verify all generator outputs of your HEAD commit as it would merge with master. These must match the expectations made by your contribution. You may regenerate an individual generator by passing the relevant config(s) as an argument to the script, for example ./bin/generate-samples.sh bin/configs/java*. For Windows users, please run the script in Git BASH.
• File the PR against the correct branch: master (5.3.0), 6.0.x
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