Hide cinder CLI errors on bash-completion

On my environment, the cinderclient CLI reports:
/usr/lib/python2.7/site-packages/requests/__init__.py:91:
RequestsDependencyWarning: urllib3 (1.25.6) or
chardet (2.2.1) doesn't match a supported version!

When running any command.

This is fairly irritating to have pop up in the
context of cinder bash-completion calls, i.e.,
when you hit tab after "cinder" at the shell.

Just hide errors there rather than pollute the
screen with them.

Change-Id: I40019dcc845015de8cfe8165656829cdaa446666

tools/cinder.bash_completion

@@ -10,7 +10,7 @@ _cinder()
     prev="${COMP_WORDS[COMP_CWORD-1]}"
 
     if [ "x$_cinder_opts" == "x" ] ; then
-                cbc="`cinder bash-completion | sed -e "s/  *-h  */ /" -e "s/  *-i  */ /"`"
+                cbc="`cinder bash-completion 2>/dev/null | sed -e "s/  *-h  */ /" -e "s/  *-i  */ /"`"
                 _cinder_opts="`echo "$cbc" | sed -e "s/--[a-z0-9_-]*//g" -e "s/  */ /g"`"
                 _cinder_flags="`echo " $cbc" | sed -e "s/ [^-][^-][a-z0-9_-]*//g" -e "s/  */ /g"`"
      fi