SET_THREAD_NAME when thread is started

rather than in parent thread after thread creation
to eliminate race between setting thread name and first
log message

Signed-off-by: Hal Rosenstock <hal@mellanox.com>
[distrib acm].c: Set main thread name for log and debug purposes

rather than thread ID

In core plugin, this was left as thread ID
due to multithreads there from OpenSM.

Signed-off-by: Hal Rosenstock <hal@mellanox.com>