libhwminijail from hardware/interfaces to libhidl.

This library is not a hardware interface, so it doesn't
belong directly in hardware/interfaces. Moving it to
libhidl because it is intended to be a helper library for
hal implementations that want to use minijail/seccomp.

Test: pass
Change-Id: I3f9503f491788492c6692d6584eb088e47862c7a