Revert "libbinder: require shell/root UID for shell"

This reverts commit f0f97d36.

Reason for revert: as requested by frameworks team: implementations of
    shell command should check permissions and calls to binder
    interfaces are already guarded by SELinux.

Bug: N/A
Test: N/A
Change-Id: I0f4181bb7f9fdb252644cbbcbcd099696ce150be