cilium: return formatted error on ipsec-key-file open failure
cilium: return formatted error on ipsec-key-file open failure

before this PR the cilium-agent error was not so clear:
level=fatal msg="Error while creating daemon" error="open : no such file or directory" subsys=daemon

Fixes: a7beef597d (cilium: ipsec, import keys via certs file)

Signed-off-by: Nirmoy Das <6ad020fa725fa73abb9a553bfe35b16e2f80a6a0@suse.de>

cilium/cilium,michi-covalent/cilium,tklauser/cilium,tgraf/cilium,cilium/cilium,tgraf/cilium,tklauser/cilium,tklauser/cilium,cilium/cilium,tgraf/cilium,tklauser/cilium,michi-covalent/cilium,tgraf/cilium,cilium/cilium,michi-covalent/cilium,tgraf/cilium,tklauser/cilium,michi-covalent/cilium,michi-covalent/cilium,cilium-team/cilium,cilium-team/cilium,tgraf/cilium,cilium/cilium