fix some alpine issues

2 jobs for gitlab-ci in 21 minutes and 50 seconds (queued for 1 second)
latest
Status Job ID Name Coverage
  Buildandtest
failed #728
alpine

00:11:01

failed #727
debian

00:10:48

 
Name Stage Failure
failed
debian Buildandtest
	/go/pkg/mod/gopkg.in/check.v1@v1.0.0-20180628173108-788fd7840127/check.go:781 +0x628
gopkg.in/check%2ev1.(*suiteRunner).forkCall.func1(0xc0000b4100, 0xc0000c10e0, 0xc000118360)
/go/pkg/mod/gopkg.in/check.v1@v1.0.0-20180628173108-788fd7840127/check.go:675 +0x98
created by gopkg.in/check%2ev1.(*suiteRunner).forkCall
/go/pkg/mod/gopkg.in/check.v1@v1.0.0-20180628173108-788fd7840127/check.go:672 +0x1fb
FAIL github.com/otrv4/otrng-prekey-server/server/raw 600.030s
FAIL
make: *** [Makefile:11: test] Error 1
ERROR: Job failed: exit code 1
failed
alpine Buildandtest
	/go/pkg/mod/gopkg.in/check.v1@v1.0.0-20180628173108-788fd7840127/check.go:781 +0x628
gopkg.in/check%2ev1.(*suiteRunner).forkCall.func1(0xc0000b4100, 0xc0000c10e0, 0xc000118360)
/go/pkg/mod/gopkg.in/check.v1@v1.0.0-20180628173108-788fd7840127/check.go:675 +0x98
created by gopkg.in/check%2ev1.(*suiteRunner).forkCall
/go/pkg/mod/gopkg.in/check.v1@v1.0.0-20180628173108-788fd7840127/check.go:672 +0x1fb
FAIL github.com/otrv4/otrng-prekey-server/server/raw 600.025s
FAIL
make: *** [Makefile:11: test] Error 1
ERROR: Job failed: exit code 2