[#10365] YSQL: TestYsqlUpgrade#upgradeIsIdempotent broken in ASAN

Summary:
When running `org.yb.pgsql.TestYsqlUpgrade#upgradeIsIdempotent` in ASAN, the following (slightly groomed) error is produced:

```
==10620==ERROR: AddressSanitizer: stack-use-after-scope on address 0x7efff21dd790 at pc 0x7f0012f16eaa bp 0x7efff21dcd30 sp 0x7efff21dcd28
READ of size 1 at 0x7efff21dd790 thread T30 (rpc_tp_TabletSe)
    #0 0x7f0012f16ea9 in std::__1::basic_string<...>::__is_long() ...
    #1 0x7f0012f16ea9 in std::__1::basic_string<...>::__get_pointer() ...
    #2 0x7f0012f16ea9 in std::__1::basic_string<...>::data() ...
    #3 0x7f0012f16ea9 in std::__1::basic_string<...>::c_str() ...
    #4 0x7f0012f16ea9 in yb::PgDeriveSocketDir(std::__1::basic_string<...> const&) yb/util/pg_util.cc:29
    #5 0x7f002863cf14 in yb::pgwrapper::YsqlUpgradeHelper::Connect(std::__1::basic_string<...> const&) yb/yql/pgwrapper/ysql_upgrade.cc:233:7
    #6 0x7f002863d6aa in yb::pgwrapper::YsqlUpgradeHelper::Upgrade() yb/yql/pgwrapper/ysql_upgrade.cc:251:24
    #7 0x7f0029043b61 in yb::tserver::TabletServiceAdminImpl::UpgradeYsql(...) yb/tserver/tablet_service.cc:1558:38
    #8 0x7f001d74316e in yb::tserver::TabletServerAdminServiceIf::Handle(...) yb/tserver/tserver_admin.service.cc:490:7
    #9 0x7f001427742d in yb::rpc::ServicePoolImpl::Handle(...) yb/rpc/service_pool.cc:260:19
    #10 0x7f00141283f0 in yb::rpc::InboundCall::InboundCallTask::Run() yb/rpc/inbound_call.cc:218:13
    #11 0x7f00142a4c2b in yb::rpc::(anonymous namespace)::Worker::Execute() yb/rpc/thread_pool.cc:105:15
    #12 0x7f0012fbcdd0 in yb::Thread::SuperviseThread(void*) yb/util/thread.cc:771:3
    #13 0x7f0007547ea4 in start_thread (/lib64/libpthread.so.0+0x7ea4)
    #14 0x7f00072709fc in __clone (/lib64/libc.so.6+0xfe9fc)
```

Apparently, `server_->pgsql_proxy_bind_address()` passed to `YsqlUpgradeHelper` constructor by reference from `TabletServiceAdminImpl::UpgradeYsql` somehow goes out of scope.
To fix this, it's now passed by value.

Test Plan: ybd asan --java-test org.yb.pgsql.TestYsqlUpgrade#upgradeIsIdempotent

Reviewers: sergei, mihnea, jason, dmitry

Reviewed By: dmitry

Subscribers: bogdan, yql

Differential Revision: https://phabricator.dev.yugabyte.com/D13557

src/yb/tserver/tablet_server.h

@@ -210,7 +210,7 @@ class TabletServer : public DbServerBase, public TabletServerIf {
     return log_prefix_;
   }
 
-  const HostPort pgsql_proxy_bind_address() const { return pgsql_proxy_bind_address_; }
+  const HostPort& pgsql_proxy_bind_address() const { return pgsql_proxy_bind_address_; }
 
   client::LocalTabletFilter CreateLocalTabletFilter() override;