bpf,datapath: map-migrate - specify full tc/globals/ bpffs path
bpf,datapath: map-migrate - specify full tc/globals/ bpffs path

This patch fixes bpffs migrations meant to occur at runtime. The tc/globals/
part of the path was missing, and the bpffs root was being scanned instead,
causing migrations not to run. This would lead to endpoints continuously
failing to regenerate at runtime when map definitions in the ELF differ from
their pinned counterparts, e.g. during an agent upgrade.

For example, when resizing CALLS_MAP and trying to replace a program, the old
map will be loaded from bpffs, while the program expects to see a map of a
different capacity:

```
~ tc filter replace dev cilium-probe ingress bpf da obj bpf/bpf_lxc.o sec from-container
libbpf: couldn't reuse pinned map at '/sys/fs/bpf/tc//globals/test_cilium_calls_65535': parameter mismatch
libbpf: map 'test_cilium_calls_65535': error reusing pinned map
libbpf: map 'test_cilium_calls_65535': failed to create: Invalid argument(-22)
libbpf: failed to load object 'bpf/bpf_lxc.o'
Unable to load program
```

The CLI equivalent executed as part of init.sh does work as expected, as the
full path including tc/globals/ is specified there.

Signed-off-by: Timo Beckers <98c2d5a1e48c998bd9ba9dbc53d6857beae1c9bd@isovalent.com>

michi-covalent/cilium,michi-covalent/cilium,cilium/cilium,michi-covalent/cilium,michi-covalent/cilium,cilium/cilium,cilium/cilium,cilium/cilium,cilium/cilium,michi-covalent/cilium