ipk: Decode byte data to string in manifest handling
```
File: '/home/andrew/src/openbmc/openbmc/meta/lib/oe/package_manager/ipk/manifest.py', lineno: 69, function: create_full
0065: output = pm.dummy_install(pkgs_to_install)
0066:
0067: with open(self.full_manifest, 'w+') as manifest:
0068: pkg_re = re.compile('^Installing ([^ ]+) [^ ].*')
*** 0069: for line in set(output.split('\n')):
0070: m = pkg_re.match(line)
0071: if m:
0072: manifest.write(m.group(1) + '\n')
0073:
Exception: TypeError: a bytes-like object is required, not 'str'
```
Change-Id: Ifefb13bfa22c766d20ab9f73f7abe5163b3df86f Signed-off-by: Andrew Jeffery <andrew@aj.id.au> Signed-off-by: Richard Purdie <richard.purdie@linuxfoundation.org>
