Address python3 string issues with subprocess

This patch updates our Popen call to enable
newlines for calls that we parse or consume the output for.
Without universal_newlines=True, the output is treated as bytes
under python3 which leads to issues later where we are using it as
strings.

See https://docs.python.org/3/glossary.html#term-universal-newlines

Story: 2006796
Task: 42696

Signed-off-by: Charles Short <charles.short@windriver.com>
Change-Id: I9b93907c05486b1f76aebe181af812c243285d6a

ceph/ceph/files/ceph-manage-journal.py

@@ -25,6 +25,7 @@ def command(arguments, **kwargs):
         arguments,
         stdout=subprocess.PIPE,
         stderr=subprocess.PIPE,
+        universal_newlines=True,
         **kwargs)
     out, err = process.communicate()
     return out, err, process.returncode