RFR 8139373 : [TEST_BUG] java/net/MulticastSocket/MultiDead.java failed with timeout

[Ivan Gerasimov]

Hello!

A few failures of the recently added regtest were observed.
The failures seem to be due to slow machines.

The suggested fix is to
1) increase the timeout,
2) take into account the timeout factor from the jtreg's settings,
3) measure the time of individual cycle of the loop, and give up, if it 
appeared to be too slow.

BUGURL: https://bugs.openjdk.java.net/browse/JDK-8139373
WEBREV: http://cr.openjdk.java.net/~igerasim/8139373/00/webrev/

Would you help review this fix?

Sincerely yours,
Ivan