iwlwifi: fix scan race

iwlwifi: fix scan race

There is a problem if an "internal short scan" is in progress when a
mac80211 requested scan arrives. If this new scan request arrives within
the "next_scan_jiffies" period then driver will immediately return success
and complete the scan. The problem here is that the scan has not been
fully initialized at this time (is_internal_short_scan is still set to true
because of the currently running scan), which results in the scan
completion never to be sent to mac80211. At this time also, evan though the
internal short scan is still running the state (is_internal_short_scan)
will be set to false, so when the internal scan does complete then mac80211
will receive a scan completion.

Fix this by checking right away if a scan is in progress when a scan
request arrives from mac80211.

Signed-off-by: Reinette Chatre <reinette.chatre@intel.com>