vty.py: Fix endl removed when pkt buffer content ends exactly on a newline char

As a result, osmo_interact_vty.py was printing incorrect output:
"""
-        <param name='shutdown' doc='Remove the APN from administrative shut-down' />
-      </params>
+        <param name='shutdown' doc='Remove the APN from administrative shut-down' />      </params
"""

Change-Id: Ib1dbf39db1b27331ea4c39051e550a87780d9f76
1 file changed