Make NDC not block forever and handle restart.

Need changes in core.

Still possible for netd to get wedged but system won't die because of it.
Leads the way to having forking netd - then only individual commands would
wedge, promoting stability.

bug:5864209
Change-Id: Ifcd37511c8239fe3df7e9070869b63a9c5649bd2
2 files changed