linktest should not generate stdout output for serial retests, when the number of serial retests are 0
When executing linktest without any serial tests command line output is still generated. This should be removed, or at least adapted to not give NANs. Here is an example output:
RESULT: Min Time Stest: 0.00000000us ( 0.00 MiB/s) [iter 1 ] RESULT: Max Time Stest: 0.00000000us ( 0.00 MiB/s) [iter 1 ] RESULT: Avg Time Stest: -nanus ( -nan MiB/s) [iter 1 ]