[C#][netcore] Fix package name in the localVar types

Created by: etherealjoy

PR checklist

• Read the contribution guidelines.
• Ran the shell script under ./bin/ to update Petstore sample so that CIs can verify the change. (For instance, only need to run ./bin/{LANG}-petstore.sh, ./bin/openapi3/{LANG}-petstore.sh, ./bin/security/{LANG}-petstore.sh and ./bin/openapi3/security/{LANG}-petstore.sh if updating the {LANG} (e.g. php, ruby, python, etc) code generator or {LANG} client's mustache templates). Windows batch files can be found in .\bin\windows\.
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Description of the PR

• when package name is set the generated code fails to compile
• fix small typo ConentType

e.g.

java -jar modules/openapi-generator-cli/target/openapi-generator-cli.jar generate \
-i ~/api-specs/swagger.yaml  -o ~/genclient -g csharp-netcore \
--additional-properties packageName=MyPackage \
--additional-properties netCoreProjectFile=true \
--additional-properties targetFramework=netcoreapp2.0

cc: @wing328 @jimschubert