OSPatching - Doesn't work on RHEL

The OSPatching extension is failing when its sent public or protected settings from Azure CLI 2.0 (Python). Below are the repro steps for RHEL 7.3.

`$ cat scheduled_patch.json`
{
"disabled": false,
"stop": false,
"rebootAfterPatch": "RebootIfNeed",
"intervalOfWeeks": "1",
"dayOfWeek": "Sunday|Wednesday",
"startTime": "03:00",
"category": "ImportantAndRecommended",
"installDuration": "00:30"
}

**Azure CLI 2.0 (Python):**
`$ az vm extension set -g wjack-linux --vm-name my-vm -n OSPatchingForLinux --publisher Microsoft.OSTCExtensions --protected-settings scheduled_patch.json --version 2.3`

2017/04/04 04:35:29 [Microsoft.OSTCExtensions.OSPatchingForLinux-1.0]Config decoded correctly.
2017/04/04 04:35:29 ERROR:[Microsoft.OSTCExtensions.OSPatchingForLinux-1.0]Failed to enable the extension with error: 'unicode' object has no attribute 'copy', stack trace: Traceback (most recent call last):
2017/04/04 04:35:29 ERROR: File "/var/lib/waagent/Microsoft.OSTCExtensions.OSPatchingForLinux-2.3.0.1/./handler.py", line 63, in enable
2017/04/04 04:35:29 ERROR: settings = protected_settings.copy()
2017/04/04 04:35:29 ERROR:AttributeError: 'unicode' object has no attribute 'copy'

Start with handler.py at line 63 and reproduce the failure using the provided az vm extension set command and scheduled_patch.json on RHEL 7.3. Done means the OSPatching extension accepts the protected or public settings and enables without the reported AttributeError.

Written by the indexing model from the issue text.