term pty fd - properly shut down without a 100% cpu hang
term pty fd - properly shut down without a 100% cpu hang

i've noticed that the exe cb tries to drain the pty fd but reads
return -1 with EAGAIN so terminology just spins forever in cpu trying
to drain a buffer that does not drain, so make a special case on exe
exit - drain until there just is nothing else to read then give up.

@fix

godfath3r/terminology,godfath3r/terminology,godfath3r/terminology