Fixed to wait the child process of fork(2).
Fixed to wait the child process of fork(2).

Sometimes the SIGNALED command came to a child which had not connected
with the mhub.

SumiTomohiko/fsyscall2,SumiTomohiko/fsyscall2,SumiTomohiko/fsyscall2,SumiTomohiko/fsyscall2,SumiTomohiko/fsyscall2