vndk: remove vendor/lib from the search path of the 'vndk' namespace

'vndk' namespace is the place for VNDK-SP libs. So /vendor/lib must be
removed from its search paths. It was there just because libhardware
(which is VNDK-SP) is loading HAL libs in vendor partition from there.
However this problem has been solved by modifying the libhardware so
that HAL libs are loaded from the 'sphal' namespace and not from the
current (the 'vndk') namespace.

Bug: 37731053
Test: sailfish builds and boots
Change-Id: Ia88934a975aa8811e05b5ba408e42d132f20f4e9