Assertion (memory leak) in ntcf_system.t TC 28 (SunOS, select, dynamic load balancing)

[smtrfnv]

Sometimes there is an assertion happening in ntcf_system.t TC 28, it appears only on SunOS when select driver is used and dynamic load balancing is enabled.

[ W ][ 31JUL2023_13:13:04.846 ][             main ][                   ntcf_system.t.cpp:9054 ]: ETIMEDOUT/ECONNREFUSED/ECONNABORTED (x100) (instantaneous)
[ F ][ 31JUL2023_13:13:05.157 ][             main ][                  ntcf_system.t.cpp:11084 ]: Assertion failed: ta.numBlocksInUse() == 0

[smtrfnv]

There is a race condition occuring during ntcr::Interface::shutdown() process.
Scenario is the following:

1. resolver->shutdown(); is called. Which leads to the ntcdns::System::shutdown() execution.
   ntcdns::System::shutdown() does not drain its d_threadPool_sp or wait for complition of all enqued jobs, it justs sets d_state to e_STATE_STOPPING state.
2. resolver->shutdown(); then stops all reactor threads.
3. It can happen that all reactor threads manage to stop earlier than all ntcdns::System resolver jobs are processed. And when the last reactor thread is deregistered from the reactor it flushes it.
4. ntcdns::System jobs are processed. The results of processing with E_CANCELLED status are pushed to the only one strand, but this strand is never processed by reactor threads, as they are stopped. Thus ntcr::StreamSocket, ntcr::Strand and the resolver itself are not deleted (as callback itself contain pointers to them)