Resolve cgroup inode in fanotify as soon as possible

[bobrik]

In #264 we reduced the amount of syscalls, here we reorder them to get the inode first.

Before:

ivan@vm:~$ sudo strace -f -TT -e open_by_handle_at,newfstatat,readlinkat -p $(pidof ebpf_exporter)
strace: Process 14153 attached with 11 threads
[pid 14153] open_by_handle_at(7, {handle_bytes=8, handle_type=254, f_handle="\x36\x00\x00\x00\x00\x00\x00\x00"}, O_RDONLY) = 13 <0.000764>
[pid 14153] readlinkat(AT_FDCWD, "/proc/self/fd/13", "/sys/fs/cgroup/system.slice", 128) = 27 <0.000815>
[pid 14153] newfstatat(AT_FDCWD, "/sys/fs/cgroup/system.slice/systemd-resolved.service", {st_mode=S_IFDIR|0755, st_size=0, ...}, 0) = 0 <0.000839>

After:

ivan@vm:~$ sudo strace -f -TT -e open_by_handle_at,newfstatat,readlinkat -p $(pidof ebpf_exporter)
strace: Process 13925 attached with 10 threads
[pid 13931] open_by_handle_at(7, {handle_bytes=8, handle_type=254, f_handle="\x36\x00\x00\x00\x00\x00\x00\x00"}, O_RDONLY) = 13 <0.000700>
[pid 13931] newfstatat(13, "systemd-resolved.service", {st_mode=S_IFDIR|0755, st_size=0, ...}, 0) = 0 <0.001069>
[pid 13931] readlinkat(AT_FDCWD, "/proc/self/fd/13", "/sys/fs/cgroup/system.slice", 128) = 27 <0.000774>