qfix: begin should correctly handle reselect

[denis-tingaikin]

Description

Issue link

Fixes networkservicemesh/integration-k8s-kind#845

How Has This Been Tested?

• Added unit testing to cover
• Tested manually
• Tested by integration testing
• Have not tested

Types of changes

• Bug fix
• New functionality
• Documentation
• Refactoring
• CI

[codecov]

Codecov Report

❌ Patch coverage is 33.33333% with 2 lines in your changes missing coverage. Please review.
⚠️ Please upload report for BASE (main@7ec603e). Learn more about missing BASE report.

Files with missing lines	Patch %	Lines
pkg/networkservice/common/begin/server.go	33.33%	2 Missing ⚠️

Additional details and impacted files

@@           Coverage Diff           @@
##             main    #1485   +/-   ##
=======================================
  Coverage        ?   70.38%           
=======================================
  Files           ?      248           
  Lines           ?    11197           
  Branches        ?        0           
=======================================
  Hits            ?     7881           
  Misses          ?     2815           
  Partials        ?      501           

☔ View full report in Codecov by Sentry.
📢 Have feedback on the report? Share it here.

🚀 New features to boost your workflow:

• ❄️ Test Analytics: Detect flaky tests, report on failures, and find test suite problems.

[glazychev-art]

I'm not sure if we should set State_UP after closing.
Maybe State_DOWN?

It may also be worth moving eventFactoryServer.state into else block. In this case we can left eventFactoryServer.state == established condition:

if eventFactoryServer.state == established && 
                request.GetConnection().GetState() == networkservice.State_RESELECT_REQUESTED &&
		eventFactoryServer.request != nil && eventFactoryServer.request.Connection != nil {
		log.FromContext(ctx).Info("Closing connection due to RESELECT_REQUESTED state")
		_, closeErr := next.Server(withEventFactoryCtx).Close(withEventFactoryCtx, eventFactoryServer.request.Connection)
		if closeErr != nil {
			log.FromContext(ctx).Errorf("Can't close old connection: %v", closeErr)
		} else {
			request.GetConnection().State = networkservice.State_DOWN
	                eventFactoryServer.state = closed
		}
	}

[denis-tingaikin]

1. we may lost eventFactoryServer.state == established
2. we don't need to request a networkservice with DOWN state if we closed previous connection