test: relax timing assumption of loop_stop
test: relax timing assumption of loop_stop

The loop_stop test makes an implicit assumption about the triggering
timing of a repeating trigger, which may not hold true on slower or
virtualized machines, thus failing the test as shown at [0] and
discussed at [1].
This commit relaxes the assumption, without mandating the exact number
of runs.

[0] http://ur1.ca/fr5bw
[1] https://groups.google.com/d/msg/libuv/5-fNIC7hIAo/yqznDmwHDAIJ

Signed-off-by: Luca Bruno <d11e81b0438fe9a6fbb85b72e5bb4c36a65f49c7@debian.org>

unknownbrackets/maxcso,unknownbrackets/maxcso,unknownbrackets/maxcso,unknownbrackets/maxcso,unknownbrackets/maxcso,unknownbrackets/maxcso,unknownbrackets/maxcso