Should fix golint check error

[niusmallnan]

cmd/control/config.go:163:2: redundant if ...; err != nil check, just return error instead.
cmd/control/install.go:219:5: redundant if ...; err != nil check, just return error instead.
cmd/control/install.go:311:4: redundant if ...; err != nil check, just return error instead.
cmd/control/install.go:694:2: redundant if ...; err != nil check, just return error instead.
cmd/control/tlsconf.go:79:2: redundant if ...; err != nil check, just return error instead.
config/cloudinit/initialize/workspace.go:32:2: redundant if ...; err != nil check, just return error instead.
dfs/scratch.go:218:2: redundant if ...; err != nil check, just return error instead
dfs/scratch.go:462:2: redundant if ...; err != nil check, just return error instead.
dfs/scratch.go:590:2: redundant if ...; err != nil check, just return error instead.
hostname/hostname.go:26:2: redundant if ...; err != nil check, just return error instead.
hostname/hostname.go:58:2: redundant if ...; err != nil check, just return error instead.
netconf/netconf_linux.go:397:3: redundant if ...; err != nil check, just return error instead.
util/util.go:90:2: redundant if ...; err != nil check, just return error instead.