adb: wait for restore to complete before returning.

If we return before waiting for the other side to finish, it'll get sent
SIGHUP.

Bug: http://b/27414382
Change-Id: I93514d2242ed0d7aa93a6ec6836270dc0783506d
(cherry picked from commit d26abed750640b4225a11763510f61ade3dd225c)
1 file changed