migrate to flock for config lock

[agouin]

juju/fslock is a dead repository, and also contains the high risk LGPL3 LICENSE

I also suspect it to be cause of some of the failures to link paths with errors such as in this run:

failed to link path gaia-juno on relayer &{%!s(*testing.T=&{{{{0 0} 0 0 0 0} [] {0xc00065f1e0} false false false false map[5935222:{} 11813422:{} 11814862:{} 48341612:{} 48342117:{} 48343357:{} 48634204:{} 56393969:{}] map[github.com/cosmos/relayer/v2/internal/relayertest.(*System).MustAddChain:{} github.com/cosmos/relayer/v2/internal/relayertest.(*System).MustRun:{} github.com/cosmos/relayer/v2/internal/relayertest.(*System).MustRunWithInput:{} github.com/strangelove-ventures/interchaintest/v7.DockerSetup:{} github.com/strangelove-ventures/interchaintest/v7/internal/dockerutil.DockerSetup:{} github.com/stretchr/testify/require.Empty:{} github.com/stretchr/testify/require.NoError:{} testing.(*common).TempDir:{}] [0x5a8960 0x5a8960]  [] false false 0xc0009dd080 false 0 0 testing.tRunner 0xc00065e820 1 [5962042 5942295 5961613 5952261 56542890 4523922 4737537] TestRelayerMultiplePathsSingleProcess {13904077291003294569 532179948 0x6626ca0} 0 0xc000066960 0xc000058850 [] {0 0} /tmp/TestRelayerMultiplePathsSingleProcess4168377849 <nil> 4} false false 0xc00045e8c0}) {  %!s(uint64=0)} /tmp/TestRelayerMultiplePathsSingleProcess4168377849/001 %!s(chan error=<nil>) %!s(context.CancelFunc=<nil>)} between chains gaia-1 and juno-3: identifier cannot be blank: invalid identifier [cosmos/ibc-go/v7@v7.0.0-beta2/modules/core/24-host/validate.go:41]

See this thread and linked discussion on the topic of exposing a go internal lib through the public x modules. Since it is not public yet, the best alternative appears to be the widely used github.com/gofrs/flock with its low risk BSD-3 LICENSE.

[jtieri]

lgtm