ipmasq: Fix concurrent map access in unit tests
ipmasq: Fix concurrent map access in unit tests

Protect the ipMasqMap by sync.RWMutex to avoid the race conditions:

=== RUN   Test
fatal error: concurrent map read and map write
goroutine 33 [running]:
runtime.throw(0xc67924, 0x21)
	/home/travis/.gimme/versions/go1.14.2.linux.amd64/src/runtime/panic.go:1116 +0x72 fp=0xc000574bb0 sp=0xc000574b80 pc=0x4370d2
runtime.mapaccess2_faststr(0xb78a00, 0xc00009e810, 0xc00003a320, 0xa, 0xc000574fb8, 0x0)
	/home/travis/.gimme/versions/go1.14.2.linux.amd64/src/runtime/map_faststr.go:116 +0x47c fp=0xc000574c20 sp=0xc000574bb0 pc=0x4155bc
github.com/cilium/cilium/pkg/ipmasq.(*ipMasqMapMock).Update(0xc0001241c0, 0xc00003a2bc, 0x4, 0x4, 0xc00003a2b8, 0x4, 0x4, 0x0, 0x0)
	/home/travis/gopath/src/github.com/cilium/cilium/pkg/ipmasq/ipmasq_test.go:42 +0x6a fp=0xc000574c88 sp=0xc000574c20 pc=0xabc63a
github.com/cilium/cilium/pkg/ipmasq.(*IPMasqAgent).Update(0xc00009e870, 0x22cf4b36, 0xc630b7c75d)

Reported-by: Andre Martins <bc9800b9d52a24cce72a73dd528afed53f10e5fc@cilium.io>
Signed-off-by: Martynas Pumputis <6b0d31c0d563223024da45691584643ac78c96e8@lambda.lt>

cilium/cilium,tgraf/cilium,cilium-team/cilium,cilium/cilium,michi-covalent/cilium,tklauser/cilium,michi-covalent/cilium,michi-covalent/cilium,tgraf/cilium,tklauser/cilium,tgraf/cilium,cilium/cilium,michi-covalent/cilium,tklauser/cilium,tgraf/cilium,tgraf/cilium,michi-covalent/cilium,tgraf/cilium,tklauser/cilium,cilium-team/cilium,tklauser/cilium,cilium/cilium,cilium/cilium