fix(e2e_tests): Removing a race condition with flags in the server

[xaionaro]

The problem

2023-06-16T15:44:06.5841874Z ==================
2023-06-16T15:44:06.5841968Z WARNING: DATA RACE
2023-06-16T15:44:06.5842097Z Write at 0x000001522d18 by goroutine 52:
2023-06-16T15:44:06.5842310Z   github.com/linuxboot/contest/cmds/contest/server.initFlags()
2023-06-16T15:44:06.5842652Z       /go/src/github.com/linuxboot/contest/cmds/contest/server/server.go:81 +0x684
2023-06-16T15:44:06.5842848Z   github.com/linuxboot/contest/cmds/contest/server.Main()
2023-06-16T15:44:06.5843189Z       /go/src/github.com/linuxboot/contest/cmds/contest/server/server.go:156 +0x9c
2023-06-16T15:44:06.5843529Z   github.com/linuxboot/contest/tests/e2e.(*E2ETestSuite).startServer.func1()
2023-06-16T15:44:06.5843831Z       /go/src/github.com/linuxboot/contest/tests/e2e/e2e_test.go:130 +0x224
2023-06-16T15:44:06.5843856Z 
2023-06-16T15:44:06.5843986Z Previous read at 0x000001522d18 by goroutine 99:
2023-06-16T15:44:06.5844196Z   github.com/linuxboot/contest/cmds/contest/server.Main.func2()
2023-06-16T15:44:06.5844534Z       /go/src/github.com/linuxboot/contest/cmds/contest/server/server.go:328 +0x369
2023-06-16T15:44:06.5844543Z 
2023-06-16T15:44:06.5844666Z Goroutine 52 (running) created at:
2023-06-16T15:44:06.5844887Z   github.com/linuxboot/contest/tests/e2e.(*E2ETestSuite).startServer()
2023-06-16T15:44:06.5845327Z       /go/src/github.com/linuxboot/contest/tests/e2e/e2e_test.go:120 +0x464
2023-06-16T15:44:06.5845560Z   github.com/linuxboot/contest/tests/e2e.(*E2ETestSuite).TestPauseResume()
2023-06-16T15:44:06.5845873Z       /go/src/github.com/linuxboot/contest/tests/e2e/e2e_test.go:344 +0x21e
2023-06-16T15:44:06.5846095Z   github.com/linuxboot/contest/tests/e2e.(*E2ETestSuite).TestPauseResume()
2023-06-16T15:44:06.5846402Z       /go/src/github.com/linuxboot/contest/tests/e2e/e2e_test.go:323 +0xbd
2023-06-16T15:44:06.5846507Z   runtime.call16()
2023-06-16T15:44:06.5846728Z       /usr/local/go/src/runtime/asm_amd64.s:701 +0x48
2023-06-16T15:44:06.5846847Z   reflect.Value.Call()
2023-06-16T15:44:06.5847080Z       /usr/local/go/src/reflect/value.go:339 +0xbc
2023-06-16T15:44:06.5847374Z   github.com/stretchr/testify/suite.Run.func1()
2023-06-16T15:44:06.5847691Z       /go/pkg/mod/github.com/stretchr/[email protected]/suite/suite.go:197 +0x515
2023-06-16T15:44:06.5847799Z   testing.tRunner()
2023-06-16T15:44:06.5848046Z       /usr/local/go/src/testing/testing.go:1439 +0x24f
2023-06-16T15:44:06.5848163Z   testing.(*T).Run.func1()
2023-06-16T15:44:06.5848406Z       /usr/local/go/src/testing/testing.go:1486 +0x47
2023-06-16T15:44:06.5848415Z 
2023-06-16T15:44:06.5848539Z Goroutine 99 (finished) created at:
2023-06-16T15:44:06.5848735Z   github.com/linuxboot/contest/cmds/contest/server.Main()
2023-06-16T15:44:06.5849079Z       /go/src/github.com/linuxboot/contest/cmds/contest/server/server.go:305 +0x2b07
2023-06-16T15:44:06.5849301Z   github.com/linuxboot/contest/tests/e2e.(*E2ETestSuite).startServer.func1()
2023-06-16T15:44:06.5849616Z       /go/src/github.com/linuxboot/contest/tests/e2e/e2e_test.go:130 +0x224
2023-06-16T15:44:06.5849701Z ==================

The problem is that the flags are global. So if we have multiple end2end tests then they can have race condition on reading/writing the flags.

In this PR I make all the flags local to a specific Main() execution.