fix memory leak in trace.c

forget to free percpu variable percpu_trace_iterator
transport: cannot call debugfs_remove in transport.c
update ftrace.patch
fix oops/panic when running ktap script many times

produce panic:
- insmod ./ktapvm.ko
- endless running scripts/*.kp

then will get panic or oops, memory corrupted.

we cannot use global variable for per ktap thread.
more syscall init into library/trace.c