coredump: handle ENOBUFS and EMSGSIZE the same way

coredump: handle ENOBUFS and EMSGSIZE the same way

Depending on the runtime configuration, e.g. sysctls
net.core.wmem_default= and net.core.rmem_default and on the actual
message size, sendmsg() can fail also with ENOBUFS. E.g. alloc_skb()
failure caused by net.core.[rw]mem_default=64MiB and huge fdinfo list
from process that has 90k opened FDs.

We should handle this case in the same way as EMSGSIZE and drop part of
the message.

(cherry picked from commit 28e62e684b631f928f1d857b04f45f0d34441675)