Correct out-of order lock acquisition.
Correct out-of order lock acquisition.

Previously we had:

TFile::Open
 TFile::GetType
  TUnixSystem::IsPathLocal
   TSystem::FindHelper
    TPluginHandler::CheckForExecPlugin
     ** take the TPluginHandler lock **
      TPluginHandler::SetupCallEnv
       TClass::GetClass
        ** take the ROOT/Interpreter lock **
vs

TFile::Open
 TPluginHandler::ExecPluginImpl
  ** take the ROOT/Interpreter lock **
   TMethodCall::Execute
    ... interpreter layer
    TPluginManager::AddHandler
     ** take the TPluginHandler lock **

bbockelm/root,olifre/root,simonpf/root,olifre/root,karies/root,bbockelm/root,agarciamontoro/root,mhuwiler/rootauto,bbockelm/root,BerserkerTroll/root,mhuwiler/rootauto,mhuwiler/rootauto,BerserkerTroll/root,mhuwiler/rootauto,root-mirror/root,zzxuanyuan/root,karies/root,zzxuanyuan/root,karies/root,root-mirror/root,olifre/root,simonpf/root,agarciamontoro/root,root-mirror/root,BerserkerTroll/root,simonpf/root,BerserkerTroll/root,bbockelm/root,olifre/root,simonpf/root,simonpf/root,olifre/root,zzxuanyuan/root,agarciamontoro/root,olifre/root,mhuwiler/rootauto,mhuwiler/rootauto,zzxuanyuan/root,mhuwiler/rootauto,root-mirror/root,agarciamontoro/root,mhuwiler/rootauto,BerserkerTroll/root,bbockelm/root,davidlt/root,davidlt/root,simonpf/root,bbockelm/root,zzxuanyuan/root,agarciamontoro/root,simonpf/root,olifre/root,zzxuanyuan/root,root-mirror/root,karies/root,agarciamontoro/root,olifre/root,davidlt/root,root-mirror/root,zzxuanyuan/root,simonpf/root,mhuwiler/rootauto,root-mirror/root,olifre/root,agarciamontoro/root,bbockelm/root,BerserkerTroll/root,karies/root,davidlt/root,root-mirror/root,olifre/root,agarciamontoro/root,davidlt/root,BerserkerTroll/root,karies/root,karies/root,zzxuanyuan/root,simonpf/root,root-mirror/root,olifre/root,davidlt/root,agarciamontoro/root,bbockelm/root,simonpf/root,bbockelm/root,BerserkerTroll/root,simonpf/root,agarciamontoro/root,bbockelm/root,zzxuanyuan/root,karies/root,zzxuanyuan/root,mhuwiler/rootauto,mhuwiler/rootauto,bbockelm/root,BerserkerTroll/root,karies/root,root-mirror/root,davidlt/root,root-mirror/root,karies/root,agarciamontoro/root,davidlt/root,BerserkerTroll/root,davidlt/root,zzxuanyuan/root,zzxuanyuan/root,karies/root,davidlt/root,BerserkerTroll/root,davidlt/root