Allow cluster_connect to return false

This commit addresses GitHub Issue mit-dci#131.  That issue describes how it's
impossible to trigger the error "Failed to start coordinator client" in
sentinel_2pc::controller::init
(src/uhs/twophase/sentinel_2pc/controller.cpp) because the call to
cluster_connect in rpc::tcp_client::init always returns true.  This
commit changes the call to allow cluster_connect to return either true
or false.

Signed-off-by: Michael L. Szulczewski <[email protected]>

src/util/rpc/tcp_client.hpp

@@ -55,7 +55,7 @@ namespace cbdc::rpc {
         /// starts the response handler thread.
         /// \return true.
         [[nodiscard]] auto init() -> bool {
-            if(!m_net.cluster_connect(m_server_endpoints, false)) {
+            if(!m_net.cluster_connect(m_server_endpoints, true)) {
                 return false;
             }