netbase: always initialize m_is_unix_socket in the Proxy constructor
Summary:
This was missed in D19737, and causes a failure in the UBSAN build.
~/bitcoin-abc/src/./netbase.h:83:13: runtime error: load of value 8, which is not a valid value for type 'bool' ... UndefinedBehaviorSanitizer: invalid-bool-load ~/bitcoin-abc/src/./netbase.h:83:13
Test Plan:
cmake .. -GNinja -DENABLE_SANITIZERS=undefined -DCMAKE_C_COMPILER=clang -DCMAKE_CXX_COMPILER=clang++ ninja all check check-functional
Reviewers: #bitcoin_abc, Fabien
Reviewed By: #bitcoin_abc, Fabien
Differential Revision: https://reviews.bitcoinabc.org/D19750