Fixed search tests (#2850)
Fixed search tests (#2850)

A test was mutating the search_fields attribute of the SearchTest model causing subsequent tests that depended on the previous value to fail.
mikedingjan/wagtail,nimasmi/wagtail,kaedroho/wagtail,takeflight/wagtail,kurtw/wagtail,nilnvoid/wagtail,kurtw/wagtail,nealtodd/wagtail,Toshakins/wagtail,chrxr/wagtail,kurtrwall/wagtail,thenewguy/wagtail,mixxorz/wagtail,torchbox/wagtail,Toshakins/wagtail,rsalmaso/wagtail,iansprice/wagtail,kurtrwall/wagtail,nilnvoid/wagtail,torchbox/wagtail,kurtw/wagtail,torchbox/wagtail,rsalmaso/wagtail,nealtodd/wagtail,Toshakins/wagtail,wagtail/wagtail,iansprice/wagtail,torchbox/wagtail,mixxorz/wagtail,zerolab/wagtail,gasman/wagtail,timorieber/wagtail,nilnvoid/wagtail,thenewguy/wagtail,FlipperPA/wagtail,gasman/wagtail,timorieber/wagtail,zerolab/wagtail,FlipperPA/wagtail,nutztherookie/wagtail,takeflight/wagtail,rsalmaso/wagtail,mikedingjan/wagtail,kurtrwall/wagtail,timorieber/wagtail,FlipperPA/wagtail,rsalmaso/wagtail,jnns/wagtail,mixxorz/wagtail,zerolab/wagtail,mikedingjan/wagtail,nealtodd/wagtail,Toshakins/wagtail,wagtail/wagtail,wagtail/wagtail,kaedroho/wagtail,mixxorz/wagtail,wagtail/wagtail,chrxr/wagtail,nealtodd/wagtail,kaedroho/wagtail,nilnvoid/wagtail,nutztherookie/wagtail,nutztherookie/wagtail,zerolab/wagtail,takeflight/wagtail,wagtail/wagtail,thenewguy/wagtail,gasman/wagtail,mixxorz/wagtail,chrxr/wagtail,jnns/wagtail,iansprice/wagtail,kaedroho/wagtail,rsalmaso/wagtail,nimasmi/wagtail,nutztherookie/wagtail,timorieber/wagtail,jnns/wagtail,gasman/wagtail,iansprice/wagtail,chrxr/wagtail,kurtrwall/wagtail,jnns/wagtail,thenewguy/wagtail,nimasmi/wagtail,takeflight/wagtail,zerolab/wagtail,kaedroho/wagtail,FlipperPA/wagtail,mikedingjan/wagtail,nimasmi/wagtail,kurtw/wagtail,thenewguy/wagtail,gasman/wagtail