logwrap: wait for child process when receiving SIGINT or SIGQUIT

- Wait for the child to exit before propagating SIGINT and SIGQUIT
to the parent
- Add ignore_int_quit argument to logwrap() that gives the caller the
option to ignore SIGINT and SIGQUIT while logwrap is running

Change-Id: If5c96cf23094917211310f00aa6aed515f110f5b