[minigraph][LAG] Add LAG minigraph for Mellanox msn-2700 platform

 * new minigraph file for Mellanox platform
 * fix minigraph_facts.py to handle Mellanox msn-2700

 signed-off-by [email protected]

Author: Hrachya Mughnetsyan

ansible/inventory

@@ -3,12 +3,14 @@ switch1  ansible_host=10.0.0.100  sonic_version=v2  sonic_hwsku=ACS-S6000
 switch2  ansible_host=10.0.0.101  sonic_version=v2  sonic_hwsku=ACS-MSN2700 
 switch3  ansible_host=10.0.0.102  sonic_version=v2  sonic_hwsku=ACS-S6000   # LAG topo: 8 LAGs x 2 members/lag to spines; 16 ports to Tors
 switch4  ansible_host=10.0.0.103  sonic_version=v2  sonic_hwsku=AS7512 sonic_portsku=32x40
+switch5  ansible_host=10.0.0.104  sonic_version=v2  sonic_hwsku=ACS-MSN2700 # Minigraph targeted for MLNX platforms. LAG topo: 8 LAGs x 2 members/lag to spines; 16 ports to Tors
 
 [sonic:children]
 sonic_latest
 
 [leaf_topo_1]
 switch1
+switch5
 
 [ptf]
 ptf-1 ansible_host=10.0.0.200 ansible_ssh_user=root ansible_ssh_pass=password