Move to Alpine to fix the strange httpd error #283

Job	Run time
Build httpd+cgi image	19s
Build server image	1m 13s
Build client image	1m 10s
Run test scripts (cert_handling.sh)	2m 24s
Run test scripts (cfengine.sh)	2m 4s
Run test scripts (change_ca.sh)	1m 57s
Run test scripts (client_timing.sh)	1m 52s
Run test scripts (clones.sh)	1m 45s
Run test scripts (powershell.sh)	2m 8s
Publish httpd+cgi image	0s
Publish server image	0s
Tag and release	0s
	14m 52s

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