Basic tests for eBPF maps

Add some kernel net tests for evaluating eBPF maps. The tests verified
the basic eBPF map syscalls such as create map, update element, lookup
element and delete elements. It is prepared for further testcase
development related to xt_eBPF modules.

Add another three more test for bpf program running. Test features with
socket filter.

Test: all_tests.sh passes on android-4.4 or above

Change-Id: I25b8877c58998e712569d7922b0531852357c6b8