Fix test_inner_hashing failure due to config_db change (#7766)

KeyError: 'members' is introduced by this PR sonic-net/sonic-buildimage#13660.
In original config, we use PORTCHANNEL, now it is changed to PORTCHANNEL_MEMBER. So, the relevant test should be updated accordingly.

Test log:
  oports = []
  for ifname in ifnames:
  if po.has_key(ifname):
  oports.append([str(mg_facts['minigraph_ptf_indices'][x]) for x in po[ifname]['members']])
  E KeyError: 'members'

What is the motivation for this PR?
Fix test_inner_harhing issue

How did you do it?
PORTCHANNEL is changed to PORTCHANNEL_MEMBER

How did you verify/test it?
Run test_inner_hashing

tests/ecmp/inner_hashing/conftest.py

@@ -149,7 +149,7 @@ def build_fib(duthosts, rand_one_dut_hostname, ptfhost, config_facts, tbinfo):
     duthost.shell("redis-dump -d 0 -k 'ROUTE*' -y > /tmp/fib.{}.txt".format(timestamp))
     duthost.fetch(src="/tmp/fib.{}.txt".format(timestamp), dest="/tmp/fib")
 
-    po = config_facts.get('PORTCHANNEL', {})
+    po = config_facts.get('PORTCHANNEL_MEMBER', {})
     ports = config_facts.get('PORT', {})
 
     tmp_fib_info = tempfile.NamedTemporaryFile()
@@ -164,7 +164,7 @@ def build_fib(duthosts, rand_one_dut_hostname, ptfhost, config_facts, tbinfo):
             oports = []
             for ifname in ifnames:
                 if ifname in po:
-                    oports.append([str(mg_facts['minigraph_ptf_indices'][x]) for x in po[ifname]['members']])
+                    oports.append([str(mg_facts['minigraph_ptf_indices'][x]) for x in po[ifname]])
                 else:
                     if ifname in ports:
                         oports.append([str(mg_facts['minigraph_ptf_indices'][ifname])])