vmtest: add configs for bpf kernel selftests

vmtest is run as a TravisCI job in order to test libbpf backward compatibility
with the older kernels

Add config files required to build and run bpf kernel selftests in vmtest:
- latest.config: latest kernel config
- INDEX: links to binaries (kernels, disk image) to download
- blacklist/BLACKLIST-${kernel}: blacklisted bpf program tests for ${kernel}

travis-ci/vmtest/configs/INDEX

@@ -0,0 +1,6 @@
+INDEX	https://libbpf-vmtest.s3-us-west-1.amazonaws.com/x86_64/INDEX
+libbpf-vmtest-rootfs-2020.01.10.tar.zst	https://libbpf-vmtest.s3-us-west-1.amazonaws.com/x86_64/libbpf-vmtest-rootfs-2020.01.10.tar.zst
+vmlinux-5.5.0-rc6.zst	https://libbpf-vmtest.s3-us-west-1.amazonaws.com/x86_64/vmlinux-5.5.0-rc6.zst
+vmlinux-5.5.0.zst	https://libbpf-vmtest.s3-us-west-1.amazonaws.com/x86_64/vmlinux-5.5.0.zst
+vmlinuz-5.5.0-rc6	https://libbpf-vmtest.s3-us-west-1.amazonaws.com/x86_64/vmlinuz-5.5.0-rc6
+vmlinuz-5.5.0	https://libbpf-vmtest.s3-us-west-1.amazonaws.com/x86_64/vmlinuz-5.5.0

travis-ci/vmtest/configs/blacklist/BLACKLIST-5.5.0

@@ -0,0 +1,21 @@
+mmap
+dctcp
+cubic
+bpf_tcp_ca
+bpf_verif_scale
+cgroup_attach
+pinning
+send_signal_tracepoint_thread
+test_syncookie
+select_reuseport
+send_signal
+sockopt_inherit
+strobemeta_nounroll2
+stacktrace_build_id
+tp_attach_query
+tcp_rtt
+task_fd_query_tp
+stacktrace_map
+test_global_funcs
+skb_ctx
+fexit_bpf2bpf

travis-ci/vmtest/configs/blacklist/BLACKLIST-5.5.0-rc6

@@ -0,0 +1,18 @@
+mmap
+dctcp
+cubic
+bpf_tcp_ca
+bpf_verif_scale
+cgroup_attach
+pinning
+send_signal_tracepoint_thread
+test_syncookie
+select_reuseport
+send_signal
+sockopt_inherit
+strobemeta_nounroll2
+stacktrace_build_id
+tp_attach_query
+tcp_rtt
+task_fd_query_tp
+stacktrace_map

travis-ci/vmtest/configs/blacklist/BLACKLIST-latest

@@ -0,0 +1,23 @@
+mmap
+dctcp
+cubic
+bpf_tcp_ca
+bpf_verif_scale
+cgroup_attach
+pinning
+send_signal_tracepoint_thread
+test_syncookie
+select_reuseport
+send_signal
+sockopt_inherit
+strobemeta_nounroll2
+stacktrace_build_id
+tp_attach_query
+tcp_rtt
+task_fd_query_tp
+stacktrace_map
+fentry
+test_overhead
+kfree_skb
+fexit_stress
+fexit_test