(test suite): Don't insist on loading all completions dynamically

Some completions may already be defined from loading the main
bash_completion script, so don't insist __load_completion to always
return true when asserting presence of a completion.

test/lib/library.exp

@@ -695,7 +695,7 @@ proc init_tcl_bash_globals {} {
 # @return boolean  True (1) if completion is installed, False (0) if not.
 proc assert_install_completion_for {command} {
     set test "$command should have completion installed in bash"
-    set cmd "__load_completion $command && complete -p $command &> /dev/null && echo -n 0 || echo -n 1"
+    set cmd "__load_completion $command ; complete -p $command &> /dev/null && echo -n 0 || echo -n 1"
     send "$cmd\r"
     expect "$cmd\r\n"
     expect {