bp:MB-5307: use -Wno_improper_lists dialyzer options
bp:MB-5307: use -Wno_improper_lists dialyzer options

I.e. because we had to forker file_sorter from erlang that is not
dialyzer-clean without that option.

Orig-Reviewed-on: http://review.couchbase.org/23594

NOTE: we need to backport it, even if it's MB-5307, to keep ns_server
dialyzer clean.

Change-Id: Ifaaef60254ac751dd7cff1f2a179a0ec567ead48
Reviewed-on: http://review.couchbase.org/23670
Tested-by: Aliaksey Kandratsenka <340b8e09ca65cd3fc686427fcfed17e87eaf61e2@gmail.com>
Reviewed-by: Aliaksey Artamonau <3c875bcfb3adf2a65b2ae7686ca921e6c9433147@gmail.com>

membase/ns_server,nimishzynga/ns_server,ceejatec/ns_server,nimishzynga/ns_server,pavel-blagodov/ns_server,membase/ns_server,vzasade/ns_server,vzasade/ns_server,daverigby/ns_server,t3rm1n4l/ns_server,ceejatec/ns_server,pavel-blagodov/ns_server,daverigby/ns_server,t3rm1n4l/ns_server,mschoch/ns_server,ceejatec/ns_server,pavel-blagodov/ns_server,pavel-blagodov/ns_server,mschoch/ns_server,membase/ns_server,vzasade/ns_server,mschoch/ns_server,mschoch/ns_server,mschoch/ns_server,nimishzynga/ns_server,membase/ns_server,daverigby/ns_server,ceejatec/ns_server,nimishzynga/ns_server,t3rm1n4l/ns_server,t3rm1n4l/ns_server,ceejatec/ns_server,t3rm1n4l/ns_server,nimishzynga/ns_server,membase/ns_server,daverigby/ns_server,daverigby/ns_server,membase/ns_server,mschoch/ns_server,ceejatec/ns_server,nimishzynga/ns_server,vzasade/ns_server