Use shared library variant of libnativehelper

libnativehelper.so is now a public library and the reason the static
variant was used is now resolved (b/148645937).
already resolved.

Bug: 148645937
Bug: 150252746
Bug: 151443957
Test: m libbluetooth_jni
Change-Id: I597bf6fbcd8647a00bbf02b6d94c270cc7af133f