Fix bashism in NovaEvacuate

[Norbert Illes]

Tox syntax-check is failing because of a bashism in NovaEvacuate.

$ tox -e syntax-check
syntax-check installed:
syntax-check runtests: PYTHONHASHSEED='1152052790'
syntax-check runtests: commands[0] | bash -c /home/eillnor/work/openstack-resource-agents/utils/syntax_check.sh -a -p
possible bashism in /tmp/tmp.cRSar6D0il line 259 (<() process substituion):
        attrd_updater -n evacuate -A \
            2> >(grep -v "attribute does not exist" 1>&2) |
Syntax Test FAILED: syntax errors found in the following files:

/home/eillnor/work/openstack-resource-agents/ocf/NovaEvacuate
ERROR: InvocationError: '/bin/bash -c /home/eillnor/work/openstack-resource-agents/utils/syntax_check.sh -a -p'
__________________________________ summary __________________________________

ERROR: syntax-check: commands failed

[Adam Spiers (adam.spiers)]

It seems this can be done without bashisms: http://stackoverflow.com/questions/3618078/pipe-only-stderr-through-a-filter

[Adam Spiers (adam.spiers)]

Also http://mywiki.wooledge.org/BashFAQ/047 and http://tldp.org/LDP/abs/html/io-redirection.html

[Vincent Untz (vuntz)]

Adam: I might be wrong, but I think I found some of these links when I was trying things, and they didn't really match what is needed. But feel free to try :-)

[OpenStack Infra (hudson-openstack)]

Fix proposed to branch: master
Review: https://review.openstack.org/290543

[Norbert Illes (nilles)]

This seems ok in my manual tests, please give it a try if you can, to see if it's really work as expected.