Add extra extension file to makemessage command line

specify the file extensions of the makemessage to *.html, *.txt, *.csv

Closes-Bug: #1226910
(cherry picked from commit 0b03a7fdea3d6586ec2c22783e309bb75d68fdc5)

The above fix introduces an extra bug when updating POT files, so
the commit below is also cherry-picked.
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Fix warning in run_tests.sh --makemessages

Specify --extension=html,txt,csv only for openstack_dashboard.
For djangojs, --extension should be 'js'.
This is the cause of the warning.

Closes-Bug: #1243526
(cherry picked from commit 79ae2139bb2f458de698aa116270428f54e22dc6)
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This patch does not update POT files for stable/havana.
They will be updated in a single patch.

Change-Id: I115cd448249ac0b1b27a6b28fca3f16d6b2670a6
Merge "Add extra extension file to makemessage command line" into stable/havana