fix off-by-one errors in snprintf

fix off-by-one errors in snprintf

snprintf guarantees to always correctly place a null terminator
in the buffer string. So manually placing a null terminator
in a buffer right after a call to snprintf is redundant code.

Additionally, there is no need to use 'sizeof(buffer) - 1' in snprintf as this
means we are not using the last character in the buffer. 'sizeof(buffer)' is
enough.

Cc: stable@dpdk.org
Signed-off-by: Michael Santana <msantana@redhat.com>
Acked-by: Bruce Richardson <bruce.richardson@intel.com>
Acked-by: Anatoly Burakov <anatoly.burakov@intel.com>