CPP client compilation issues.

[tongsucn]

Describe the bug

When enabling -Wall and -Werror, the library cannot be successfully compiled:

1. Non-virtual destructor in base class: pulsar-client-cpp/lib/auth/AuthOauth2.h:47:7: error: base class 'class pulsar::CachedToken' has accessible non-virtual destructor [-Werror=non-virtual-dtor].
2. Unnecessary NULL checking on function pointer: /pulsar-client-cpp/lib/ClientImpl.cc:100:10: error: the address of 'pulsar::Logger* logger()' will never be NULL [-Werror=address].

To Reproduce

Compile with -Wall and -Werror.

Desktop (please complete the following information):

• OS: Linux
• Compiler: GCC 7.3

[smazurov]

#2 is simply wrong and can be null. GCC needs to get its act together :)

Edit: actually it can be, but it should be checking for !loggerFactory instead..