[BugFix] Fix the bug that it gets error system-mac of centec platform (…

…#12721)

Why I did it
When getting system mac of centec platform, it would increase by 1 the last byte of mac, but it could not consider the case of carry.

How I did it
Firstly, I would replace the ":" with "" of mac to a string.
And then, I would convert the mac from string to int and increase by 1, at last convert it to string with inserting ":".

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

@@ -614,9 +614,10 @@ 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