Improve robustness of consutil plugin loading (sonic-net#1353)

The configuration file does not tolerate a new line.
Enhance the plugin loading by allowing trailing chars.

Signed-off-by: Jing Kan [email protected]

Author: Staphylo

consutil/lib.py

@@ -270,8 +270,8 @@ def init_device_prefix():
 
         if os.path.exists(PLUGIN_PATH):
             fp = open(PLUGIN_PATH, 'r')
-            line = fp.readlines()
-            SysInfoProvider.DEVICE_PREFIX = "/dev/" + line[0]
+            lines = fp.readlines()
+            SysInfoProvider.DEVICE_PREFIX = "/dev/" + lines[0].rstrip()
 
     @staticmethod
     def list_console_ttys():