Bump go and container base image

- bump golang 1.17 -> 1.18
 - bump alpine 3.14 -> 3.15
 - revendor

 We need to use golang instead of golang:alpine because it does not
 contain git anymore. This should be fine as we are not enabling CGO,
 thus not linking against musl instead of libc.

Signed-off-by: leonnicolas <leonloechner@gmx.de>

Makefile

@@ -45,8 +45,8 @@ KUBECTL_BINARY := $(shell pwd)/bin/kubectl
 BASH_UNIT := $(shell pwd)/bin/bash_unit
 BASH_UNIT_FLAGS :=
 
-BUILD_IMAGE ?= golang:1.17.1-alpine3.14
-BASE_IMAGE ?= alpine:3.14
+BUILD_IMAGE ?= golang:1.18
+BASE_IMAGE ?= alpine:3.15
 
 build: $(BINS)