build: Remove docker-images lock
build: Remove docker-images lock

A single image build could block all other tests hence it was removed.

Originally it was intended from preventing double builds i.e. two build
jobs starting at roughly the same time building the same image.

mpranj/libelektra,e1528532/libelektra,e1528532/libelektra,ElektraInitiative/libelektra,mpranj/libelektra,petermax2/libelektra,BernhardDenner/libelektra,e1528532/libelektra,mpranj/libelektra,petermax2/libelektra,BernhardDenner/libelektra,petermax2/libelektra,BernhardDenner/libelektra,e1528532/libelektra,mpranj/libelektra,ElektraInitiative/libelektra,petermax2/libelektra,BernhardDenner/libelektra,petermax2/libelektra,ElektraInitiative/libelektra,ElektraInitiative/libelektra,ElektraInitiative/libelektra,petermax2/libelektra,mpranj/libelektra,BernhardDenner/libelektra,mpranj/libelektra,ElektraInitiative/libelektra,ElektraInitiative/libelektra,BernhardDenner/libelektra,e1528532/libelektra,BernhardDenner/libelektra,ElektraInitiative/libelektra,mpranj/libelektra,e1528532/libelektra,ElektraInitiative/libelektra,mpranj/libelektra,e1528532/libelektra,petermax2/libelektra,petermax2/libelektra,e1528532/libelektra,BernhardDenner/libelektra,mpranj/libelektra,mpranj/libelektra,petermax2/libelektra,ElektraInitiative/libelektra,BernhardDenner/libelektra,ElektraInitiative/libelektra,mpranj/libelektra