WebApp: Addding Source Control may fail intermittently if the request is sent while the SCM\Kudu WebSite is restarting.

## Issue Description:
The customer is using the Azure Management Libraries for Java to create a Function App.

``` oSvcMgr = m_oCliLong.appServices();
oFctApps = oSvcMgr.functionApps();
oFctApp = oFctApps.define(zFctID)
.withRegion(AzureDefs.AZURE_REGION)
.withNewResourceGroup(zResGroup)
.withPlatformArchitecture(PlatformArchitecture.X64)
.withNetFrameworkVersion(NetFrameworkVersion.V4_6)
.withAppSettings(oAzureEnv)
.defineSourceControl()
.withPublicGitRepository(AzureDefs.AZURE_FUNCTION_GITHUB_URL)
.withBranch("master")
.attach()
.defineAuthentication()
.withAnonymousAuthentication()
.attach()
.create();

if (oFctApp == null)
{
s_oLog.error("AzureFunction::createFunction Cannot create function [" + zFctID + "]");
return (false);
}
```

## Expected Result
That the Function App be configured with the Git repository.

## Actual Result
The Function App is created but without the Source Control information.

## Issue Details

While the Azure App Service Function App is being provisioned there is a time when the request to Update the Source Control may return a 500 Server error while the Site is restarting. The normal response is a 204.

This issue is opened to see if the Management Libraries can be more resilient in attempting this operation.

Start with the Azure Management Libraries for Java Function App creation flow shown in the issue, especially defineSourceControl().withPublicGitRepository().withBranch().attach(). Examine how the source-control update handles a transient 500 while the SCM/Kudu site restarts, using the expected 204 response as the success condition. Done means the created Function App retains its Git source-control configuration in this scenario.

索引モデルが issue の本文から書いたものです。