Upgrade Alpine version for both Dockerfiles (3.0)

... to improve/mitigate performance problems, see #2299. (musl libc vs. glibc)

Same PR as for 3.1dev branch: #2306

Author: drwetter

Dockerfile

@@ -1,4 +1,4 @@
-FROM alpine:3.15
+FROM alpine:3.17
 
 RUN apk update && \
     apk upgrade && \

Dockerfile.git

@@ -1,6 +1,6 @@
 # Build using git repo
 
-FROM alpine:3.15
+FROM alpine:3.17
 
 WORKDIR /home/testssl