[lldb] Fix initialization of LazyBool/bool variables m_overwrite/m_overwrite_lazy. NFCI.

This silences a GCC warning after
1f7b58f2 / D122680:

lldb/source/Commands/CommandObjectCommands.cpp:1650:22: warning: enum constant in boolean context [-Wint-in-bool-context]
 1650 |   bool m_overwrite = eLazyBoolCalculate;
      |                      ^~~~~~~~~~~~~~~~~~

Differential Revision: https://reviews.llvm.org/D123204