Configure the number of concurrency for ifmap to 100

This commit adds a concurrency setting for the ifmap client
to accept concurrent connections.

Co-Authored-By: Edouard Thuleau <edouard.thuleau@cloudwatt.com>
Signed-off-by: Sahid Orentino Ferdjaoui <sahid.ferdjaoui@cloudwatt.com>
Merge pull request #23 from sahid/master

Configure the number of concurrency for ifmap to 100
xen: Fix build break

python fetch_packages.py breaks in xen builder as xen doesn't have npm tool. This is not even
required in xen builder. Hence adding fix to catch OSError (thrown if it can't find npm) and
bailout gracefully.

Signed-off-by: Anirban Chakraborty <abchak@juniper.net>
Merge pull request #24 from anirban-c/master

xen: Fix build break
readme file