shell: directory access to sysfs_net

This will allow bionic cts test to list network interfaces in
/sys/class/net.

Bug: 70537905
Test: adb shell /data/nativetest/bionic-unit-tests/bionic-unit-tests
--gtest_filter=ifaddrs.getifaddrs_interfaces
Change-Id: Ie07425fc54f9101e911962142824697e64d2bc45