2245: phase: omit print of post-lb stats when no migration

[nlslatt]

Fixes #2245

[github-actions]

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PR tests (gcc-8, ubuntu, mpich, address sanitizer)

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PR tests (gcc-10, ubuntu, openmpi, no LB)

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PR tests (nvidia cuda 11.2, gcc-9, ubuntu, mpich)

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/vt/src/vt/pipe/pipe_manager.impl.h(133): warning: missing return statement at end of non-void function "vt::pipe::PipeManager::makeSend<f,Target>(Target) [with f=&vt::vrt::collection::lb::GreedyLB::collectHandler, Target=vt::objgroup::proxy::ProxyElm<vt::vrt::collection::lb::GreedyLB>]"
          detected during:
            instantiation of "auto vt::pipe::PipeManager::makeSend<f,Target>(Target) [with f=&vt::vrt::collection::lb::GreedyLB::collectHandler, Target=vt::objgroup::proxy::ProxyElm<vt::vrt::collection::lb::GreedyLB>]" 
/vt/src/vt/objgroup/proxy/proxy_objgroup.impl.h(202): here
            instantiation of "vt::objgroup::proxy::Proxy<ObjT>::PendingSendType vt::objgroup::proxy::Proxy<ObjT>::reduce<f,Op,Target,Args...>(Target, Args &&...) const [with ObjT=vt::vrt::collection::lb::GreedyLB, f=&vt::vrt::collection::lb::GreedyLB::collectHandler, Op=vt::collective::PlusOp, Target=vt::objgroup::proxy::ProxyElm<vt::vrt::collection::lb::GreedyLB>, Args=<vt::vrt::collection::lb::GreedyPayload>]" 
/vt/src/vt/vrt/collection/balance/greedylb/greedylb.cc(222): here

/vt/src/vt/pipe/pipe_manager.impl.h(133): warning: missing return statement at end of non-void function "vt::pipe::PipeManager::makeSend<f,Target>(Target) [with f=&MyObj::handler, Target=vt::objgroup::proxy::ProxyElm<MyObj>]"
          detected during instantiation of "auto vt::pipe::PipeManager::makeSend<f,Target>(Target) [with f=&MyObj::handler, Target=vt::objgroup::proxy::ProxyElm<MyObj>]" 
/vt/examples/callback/callback.cc(147): here

/vt/src/vt/pipe/pipe_manager.impl.h(133): warning: missing return statement at end of non-void function "vt::pipe::PipeManager::makeSend<f,Target>(Target) [with f=&colHan, Target=vt::vrt::collection::VrtElmProxy<MyCol, vt::Index1D>]"
          detected during instantiation of "auto vt::pipe::PipeManager::makeSend<f,Target>(Target) [with f=&colHan, Target=vt::vrt::collection::VrtElmProxy<MyCol, vt::Index1D>]" 
/vt/examples/callback/callback.cc(153): here

/vt/src/vt/pipe/pipe_manager.impl.h(133): warning: missing return statement at end of non-void function "vt::pipe::PipeManager::makeSend<f,Target>(Target) [with f=&MyObj::handler, Target=vt::objgroup::proxy::ProxyElm<MyObj>]"
          detected during instantiation of "auto vt::pipe::PipeManager::makeSend<f,Target>(Target) [with f=&MyObj::handler, Target=vt::objgroup::proxy::ProxyElm<MyObj>]" 
/vt/examples/callback/callback.cc(147): here

/vt/src/vt/pipe/pipe_manager.impl.h(133): warning: missing return statement at end of non-void function "vt::pipe::PipeManager::makeSend<f,Target>(Target) [with f=&colHan, Target=vt::vrt::collection::VrtElmProxy<MyCol, vt::Index1D>]"
          detected during instantiation of "auto vt::pipe::PipeManager::makeSend<f,Target>(Target) [with f=&colHan, Target=vt::vrt::collection::VrtElmProxy<MyCol, vt::Index1D>]" 
/vt/examples/callback/callback.cc(153%0D%0A%0D%0A%0D%0A ==> And there is more. Read log. <==

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