Change UniquePtr to std::unique_ptr

UniquePtr.h in libnativehelper/include is deprecated and will be removed
soon. Switching to the standard std::unique_ptr.

(cherry picked from commit 4e7d18a72f72967a881bcdf78167011a836538ef)

Bug: 63686260
Test: builds, cmd works in the device.
Merged-In: Ib008acd1dd7dba2305b0797c9dc7bab1aa747e7d
Change-Id: Ib008acd1dd7dba2305b0797c9dc7bab1aa747e7d
1 file changed