Strip exec_dirs prefix from rootwrap filters

Make the rootwrap filters more portable by removing
the explicit exec_dirs prefix from them. This allows
a binary to be installed in any of the exec_dirs and
still be used by rootwrap, which improves cross-distro
portability.

Change-Id: Ieccb8c480e0e116a976d0920ab900305a5615015
Merge "Strip exec_dirs prefix from rootwrap filters"