MLRsearch: Increase timeout to 20 minutes

MLRsearch: Increase timeout to 20 minutes

There are sporadic failures due to timeout.
An earlier edit changed how the timeout is applied
(now it is for the whole search, previously it was for final phase only)
so failures are not unexpected.

Increasing timeout value from 12 minutes to 20 minutes
(both for NDRPDR and for NDR part of RECONF)
as the frequency shows it will not prolong runs much.

The timeout is increased both in Robot call site
and in Python keyword default argument.

Change-Id: I3f07125ba9eeb90ce5819b1450044441b8b3977a
Signed-off-by: Vratko Polak <vrpolak@cisco.com>