Get rid of additional newline append

This looks like it was just incorrectly done before. writelines()
expects you to take care of newlines yourself, so each element should
end in a newline. But we were doing two separate writes, one with the
key=value pair and one with a newline

salt/modules/mac_sysctl.py

@@ -179,13 +179,10 @@ def persist(name, value, config='/etc/sysctl.conf', apply_change=False):
                     rest = rest[len(rest_v):]
                 if rest_v == value:
                     return 'Already set'
-                new_line = '{0}={1}\n'.format(name, value)
-                nlines.append(new_line)
-                nlines.append('\n')
+                nlines.append('{0}={1}\n'.format(name, value))
                 edited = True
     if not edited:
         nlines.append('{0}={1}\n'.format(name, value))
-        nlines.append('\n')
     nlines = [salt.utils.stringutils.to_str(_l) for _l in nlines]
     with salt.utils.files.fopen(config, 'w+') as ofile:
         ofile.writelines(nlines)

tests/unit/modules/test_mac_sysctl.py

@@ -96,7 +96,6 @@ class DarwinSysctlTestCase(TestCase, LoaderModuleMockMixin):
             '# Kernel sysctl configuration\n',
             '#\n',
             'net.inet.icmp.icmplim=50\n',
-            '\n',
         ])]
         with patch('salt.utils.files.fopen', mock_open(read_data=to_write)) as m_open, \
                 patch('os.path.isfile', MagicMock(return_value=True)):