Issue #3: default to ca-key.pem for key in serve
Issue #3: default to ca-key.pem for key in serve

thesamet/cfssl,thesamet/cfssl,j-delaney/cfssl,bifurcation/cfssl,jsha/cfssl,ch684/cfssl,haneric21/cfssl,ch684/cfssl,dhiltgen/cfssl,rolandshoemaker/cfssl,endocode/cfssl,ekristen/cfssl,geligaoli/cfssl,APTy/cfssl,sfurman3/cfssl,cloudflare/cfssl,letsencrypt/cfssl,cloudflare/cfssl,mclem/cfssl,wl2002/cfssl,sdgdsffdsfff/cfssl,ekristen/cfssl,drcapulet/cfssl,codyli520/cfssl,sfurman3/cfssl,rolandshoemaker/cfssl,haneric21/cfssl,cloudflare/cfssl,wl2002/cfssl,geligaoli/cfssl,thesamet/cfssl,sdgdsffdsfff/cfssl,j-delaney/cfssl,letsencrypt/cfssl,terinjokes/cfssl,drcapulet/cfssl,j-delaney/cfssl,rolandshoemaker/cfssl,haneric21/cfssl,endocode/cfssl,mclem/cfssl,geligaoli/cfssl,geligaoli/cfssl,sfurman3/cfssl,codyli520/cfssl,mitchcapper/cfssl,drcapulet/cfssl,jmhodges/cfssl,thesamet/cfssl,terinjokes/cfssl,ch684/cfssl,mitchcapper/cfssl,mitchcapper/cfssl,gtank/cfssl,drcapulet/cfssl,bifurcation/cfssl,BugRoger/cfssl,sfurman3/cfssl,dhiltgen/cfssl,j-delaney/cfssl,sdgdsffdsfff/cfssl,wl2002/cfssl,ekristen/cfssl,rolandshoemaker/cfssl,jmhodges/cfssl,APTy/cfssl,geligaoli/cfssl,ekristen/cfssl,dhiltgen/cfssl,sdgdsffdsfff/cfssl,sfurman3/cfssl,terinjokes/cfssl,letsencrypt/cfssl,codyli520/cfssl,dhiltgen/cfssl,endocode/cfssl,APTy/cfssl,BugRoger/cfssl,wl2002/cfssl,bossjones/cfssl,APTy/cfssl,terinjokes/cfssl,gtank/cfssl,bossjones/cfssl,j-delaney/cfssl,gtank/cfssl,codyli520/cfssl,endocode/cfssl,endocode/cfssl,jmhodges/cfssl,drcapulet/cfssl,bifurcation/cfssl,BugRoger/cfssl,haneric21/cfssl,cloudflare/cfssl,jsha/cfssl,letsencrypt/cfssl,bossjones/cfssl,mclem/cfssl,jsha/cfssl,BugRoger/cfssl,APTy/cfssl,wl2002/cfssl,ch684/cfssl,gtank/cfssl,rolandshoemaker/cfssl,jmhodges/cfssl,codyli520/cfssl,bossjones/cfssl,bifurcation/cfssl,mclem/cfssl,dhiltgen/cfssl,haneric21/cfssl,mclem/cfssl