[BugFix] Fix the bug that it gets error system-mac of centec platform (#12721) (#13625)

src/sonic-py-common/sonic_py_common/device_info.py

@@ -647,9 +647,10 @@ def get_system_mac(namespace=None):
 
     # Align last byte of MAC if necessary
     if version_info and version_info['asic_type'] == 'centec':
-        last_byte = mac[-2:]
-        aligned_last_byte = format(int(int(last_byte, 16) + 1), '02x')
-        mac = mac[:-2] + aligned_last_byte
+        mac_tmp = mac.replace(':','')
+        mac_tmp = "{:012x}".format(int(mac_tmp, 16) + 1)
+        mac_tmp = re.sub("(.{2})", "\\1:", mac_tmp, 0, re.DOTALL)
+        mac = mac_tmp[:-1]
     return mac