SocketManager: fix timeslice exceeded log message

Reviewer: trivial

We were passing a 64-bit int to printf where it expected a 32-bit int, so on 
some architectures the varargs were interpreted incorrectly.

This would have been caught by the GCC `format` attribute. I attempted to add
this attribute to aim_log_common but it raised errors for format strings using
the AIM datatype syntax.