log: fix level/type retrieving from a standard thread

log: fix level/type retrieving from a standard thread

The functions rte_log_cur_msg_loglevel() and rte_log_cur_msg_logtype()
return the current log level/type for the message being processed. They
are used when implementing a user-defined logging stream.

The current log levels and types were stored in a table indexed by the
lcore_id, only returning a valid value for dataplane threads. Setting
and getting these values in a non dataplane thread was ignored, using
the global value instead.

To fix this issue, a per-thread variable could be used (with
RTE_DEFINE_PER_LCORE), allowing any pthread to set and retrieve its
current log level or type.

Signed-off-by: Maxime Leroy <maxime.leroy@6wind.com>
Signed-off-by: Olivier Matz <olivier.matz@6wind.com>
Acked-by: David Marchand <david.marchand@6wind.com>