For ENG-6040, add @GC to sql command and web studio, run the gc call in a dedicated thread, return a result table with timing
Guard against invoking stopping or stopped twice
Don't set stopped outside of safeStopped
For ENG-6040, fix broken TestClientInterface.testGC
Merge pull request #1226 from VoltDB/flaky_piconetwork

Fix flaky piconetwork test (and network)
Merge pull request #1227 from VoltDB/ENG-6040

Eng 6040, add support for remotely invoked System.gc()