Touch attribute file to fix errors like:
Can't open ./demoCA/index.txt.attr for reading,
No such file or directory
140553384993216:error:02001002:system library:
fopen:No such file or directory:../crypto/bio/bss_file.c:72:
fopen('./demoCA/index.txt.attr','r')
140553384993216:error:2006D080:BIO routines:
BIO_new_file:no such file:../crypto/bio/bss_file.c:79:
Check that the request matches the signature
* fix CRL tests to work
* regenerate certificates to be at least 2048 bit
(fixes buster and rhel8 in buildbot)
* update generate-ssl-cert.sh to generate crl files
* make all SSL tests to use certificates generated
in generate-ssl-cert.sh, remove unused certificates
