acm.c: Cosmetic formatting changes

Signed-off-by: Hal Rosenstock <hal@mellanox.com>
acm.c: Move ssa_open_devices call from ctrl to main thread

Calling ssa_open_devices from main application thread allows
ibacm application to exit with an error if there is no
IB device found. This behavior is the same as original ACM (no SSA mode).
Also, it allows removing signaling from ctrl thread to main thread.

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