Assert is_l2() on sub-ints cannot have address or LCP

unittest/yaml/error-bridgedomain2.yaml

@@ -4,7 +4,8 @@ test:
     expected:
      - "bridgedomain .* member .* has an LCP"
      - "interface .* is in L2 mode but has LCP name .*"
-    count: 5
+     - "sub-interface .* is in L2 mode but has LCP name .*"
+    count: 6
 ---
 interfaces:
   GigabitEthernet1/0/0:

unittest/yaml/error-bridgedomain3.yaml

@@ -6,7 +6,8 @@ test:
      - "sub-interface .* has an address but .* does not have LCP"
      - "bridgedomain .* member .* has an address"
      - "interface .* is in L2 mode but has an address"
-    count: 8
+     - "sub-interface .* is in L2 mode but has an address"
+    count: 9
 ---
 interfaces:
   GigabitEthernet1/0/0:

unittest/yaml/error-l2xc6.yaml

@@ -4,7 +4,9 @@ test:
     expected:
      - "sub-interface .* l2xc target .* cannot have an address"
      - "sub-interface .* l2xc target .* cannot have an LCP"
-    count: 2
+     - "sub-interface .* is in L2 mode but has an address"
+     - "sub-interface .* is in L2 mode but has LCP name .*"
+    count: 4
 ---
 interfaces:
   GigabitEthernet1/0/0:

validator/interface.py

@@ -435,6 +435,9 @@ def validate_interfaces(yaml):
                     result = False
 
                 sub_lcp = get_lcp(yaml, sub_ifname)
+                if is_l2(yaml, sub_ifname) and sub_lcp:
+                    msgs.append("sub-interface %s is in L2 mode but has LCP name %s" % (sub_ifname, sub_lcp))
+                    result = False
                 if sub_lcp and not lcp.is_unique(yaml, sub_lcp):
                     msgs.append("sub-interface %s does not have a unique LCP name %s" % (sub_ifname, sub_lcp))
                     result = False
@@ -459,6 +462,9 @@ def validate_interfaces(yaml):
                     if not iface_lcp:
                         msgs.append("sub-interface %s has an address but %s does not have LCP" % (sub_ifname, ifname))
                         result = False
+                    if is_l2(yaml, sub_ifname):
+                        msgs.append("sub-interface %s is in L2 mode but has an address" % sub_ifname)
+                        result = False
                     for a in sub_iface['addresses']:
                         if not address.is_allowed(yaml, sub_ifname, sub_iface['addresses'], a):
                             msgs.append("sub-interface %s IP address %s conflicts with another" % (sub_ifname, a))