btrfs-progs: ci: fix docker-run argument parsing

The runner script allows to pass arguments to docker and the final
command, using the -- separator. This did not work as expected, the
arguments got concatenated to the first member, not all of them passed.
The following now works:

  $ ./docker-run --env CC=clang
  $ ./docker-run --env CC=clang --
  $ ./docker-run --env CC=clang -- /bin/bash

Signed-off-by: David Sterba <dsterba@suse.com>

ci/images/docker-run

@@ -1,16 +1,15 @@
 #!/bin/bash
 # Run the container
-# $0 [docker arguments] [--] [command and arguments]
+# $0 [docker arguments] [-- command and arguments]
 
 prefix=kdave
 image=$(basename `pwd` | tr '[A-Z]' '[a-z]')
 
 declare -a ARGS
-while :; do
+while [ $# -gt 0 ]; do
 	case "$1" in
 		--) shift; break;;
-		--*) ARGS+="$1"; shift;;
+		*) ARGS+=("$1"); shift;;
-		*) break;;
 	esac
 done