If AcceptorPollRate is configured in configuration
file, the default value used will be given by
ACCEPT_TIMEOUT_US. So change the default value, it
can solve the performance degradation issue of
nvmf target.
Change-Id: I867bb03dd8b2b81b86911130babd0334d9857de8
Signed-off-by: Ziye Yang <ziye.yang@intel.com>