Make the error message of alarm-not-found clear

When creating a alarm combination with invalid project, ceilometer will
raise alarm-Not-Found error, even though the specified alarm ids are
existent. The error message is easily misleading.
This change gives a explicit presentation of this case.

Change-Id: Id189209ed4ccf27543f8dc628ca5f82eeeeeaa44
Closes-bug: #1320433
Correct misspelled words

Correct some misspelled words (
"extention" => "extension",
"adress" => "address"..)

Change-Id: I192905676031d1a05fc23aa222dc061b40b44932
Don't override the original notification message

We must not override the notification message.

This patch make the code clearer by not changing the message payload
during the loop over neutron ressources.

Change-Id: Ib3d1245555c9d5e080fc0979df874ee940bed29d
Fix aggregator flush method

When no samples have been handled by the aggregator but flush method is
called, an empty array must be returned because 'initial_timestamp' have
not been set yet.

Also, the pipeline always catchs exception from transformer and when an
error occurs into a transformer the unit can not catch them.
The patch also reraises any transformer exceptions.

Closes-bug: #1325507
Co-Authored-By: Ala Rezmerita <ala.rezmerita@cloudwatt.com>

Change-Id: Ib3183dfa3ee37ba586eb03a73f5de4641dd98514
Remove --tmpdir from mktemp

This option is not portable and does not work on Darwin. The -t option
and the usage of a relative name implies anyway that $TMPDIR will be
used, on all mktemp versions.

Change-Id: I3abfc8606b37d6e2f8c5ff4dc6855a4558e8f7c9
Merge "Fix aggregator flush method"
Merge "Remove --tmpdir from mktemp"
Merge "Don't override the original notification message"
Merge "Correct misspelled words"
Merge "Make the error message of alarm-not-found clear"