[plugin] Add missing return statements

[vinokurig]

What it does

Add missing return statements to VsCodePluginDeployerResolver.
Since 2d4c845 was merged Plugins install their dependent plugins automatically.
VsCode Github plugin includes built in vscode git extension in it's dependent extensions which is not present in the vscode marketplace. This causes an error witch is not properly handled. The return statement in the catch error section allows to skip the installation of dependent extension in case of failure.

fixes eclipse-che/che#14319

How to test

1. Remove git from theia/examples/browser/package.json.
2. Download vscode git extension.
3. Download vscode github-pull-request extension.
4. Create plugins folder in Theia's root and paste the downloaded plugins to it.
5. Start Theia

Without the fix the vscode git and Github plugins fail to start.

Review checklist

• as an author, I have thoroughly tested my changes and carefully followed the review guidelines

Reminder for reviewers

• as a reviewer, I agree to behave in accordance with the review guidelines

[akosyakov]

@vinokurig does it fix #5993?

[akosyakov]

@vinokurig I think this fix is fine. Although I wonder: do you have git extension deployed already right? then we should not try to resolve it again, we have a check for the current deployment: https://github.com/theia-ide/theia/blob/master/packages/plugin-ext/src/main/node/plugin-deployer-impl.ts#L145 Maybe we should extend it and have a look into deployed state, i.e. into PluginDeployerHandler. If it is so please file an issue.

[vinokurig]

@akosyakov

@vinokurig does it fix #5993?

It partially fixes the issue, now the error is:

root ERROR Failed to resolve plugins from 'vscode:extension/eclipse-cdt.cdt-gdb-vscode' Error: No extension
    at Request._callback (/home/ivinokur/projects/theia/packages/plugin-ext-vscode/lib/node/plugin-vscode-resolver.js:121:44)
    at Request.init.self.callback (/home/ivinokur/projects/theia/node_modules/request/request.js:185:22)
    at Request.emit (events.js:198:13)
    at Request.<anonymous> (/home/ivinokur/projects/theia/node_modules/request/request.js:1161:10)
    at Request.emit (events.js:198:13)
    at IncomingMessage.<anonymous> (/home/ivinokur/projects/theia/node_modules/request/request.js:1083:12)
    at Object.onceWrapper (events.js:286:20)
    at IncomingMessage.emit (events.js:203:15)
    at endReadableNT (_stream_readable.js:1145:12)
    at process._tickCallback (internal/process/next_tick.js:63:19)

Although I wonder: do you have git extension deployed already right? then we should not try to resolve it again, we have a check for the current deployment: https://github.com/theia-ide/theia/blob/master/packages/plugin-ext/src/main/node/plugin-deployer-impl.ts#L145 Maybe we should extend it and have a look into deployed state, i.e. into PluginDeployerHandler. If it is so please file an issue.

The initial problem is fixed now by 1a3048d but I think the return is still needed in that part of code.

[akosyakov]

@vinokurig yes, let's merge, but i think we also should prevent Failed to resolve plugins from by checking already deployed plugins if possible. Could you comment findings on #5993 please?