[dbnode] Fix case insensitive regexp flag implementation for metrics …

…selector (#2564)

go.mod

@@ -65,7 +65,7 @@ require (
 	github.com/m3db/stackmurmur3 v0.0.0-20171110233611-744c0229c12e // indirect
 	github.com/m3db/tools v0.0.0-20181008195521-c6ded3f34878
 	github.com/m3dbx/pilosa v0.0.0-20200602205121-7f389745e9ab
-	github.com/m3dbx/vellum v0.0.0-20200602203954-e10aaedbd934
+	github.com/m3dbx/vellum v0.0.0-20200826162549-f94c029903de
 	github.com/mauricelam/genny v0.0.0-20180903214747-eb2c5232c885
 	github.com/mjibson/esc v0.1.0
 	github.com/opencontainers/image-spec v1.0.1 // indirect

go.sum

@@ -471,8 +471,8 @@ github.com/m3db/tools v0.0.0-20181008195521-c6ded3f34878 h1:kww0LtVVfGrXR7Ofpbi/
 github.com/m3db/tools v0.0.0-20181008195521-c6ded3f34878/go.mod h1:TxroQUZzb1wzOsq+4+TfVtT7z89YTz3v2UJAYfLNfLE=
 github.com/m3dbx/pilosa v0.0.0-20200602205121-7f389745e9ab h1:CpoDBrDayfBBuueJF+8c2iQwDKiZCw2JRB5yS1RFzJA=
 github.com/m3dbx/pilosa v0.0.0-20200602205121-7f389745e9ab/go.mod h1:muOSChOjsONKXcQTw+pr+bqIvb4bD7tSQHAXJPlerwc=
-github.com/m3dbx/vellum v0.0.0-20200602203954-e10aaedbd934 h1:INQTjUQJZlfKiHvFjACwTSTZd6TxtgoWP3am4+CmPVU=
-github.com/m3dbx/vellum v0.0.0-20200602203954-e10aaedbd934/go.mod h1:DOTAUfV4bzK6Nrb0dboT/oCG0DnQuX+/n0jfZPh6xxI=
+github.com/m3dbx/vellum v0.0.0-20200826162549-f94c029903de h1:C4DpCfTNzJf5RhJqxOtfWAnD2d6ls7KDnK1boBGUnVg=
+github.com/m3dbx/vellum v0.0.0-20200826162549-f94c029903de/go.mod h1:DOTAUfV4bzK6Nrb0dboT/oCG0DnQuX+/n0jfZPh6xxI=
 github.com/magiconair/properties v1.8.1 h1:ZC2Vc7/ZFkGmsVC9KvOjumD+G5lXy2RtTKyzRKO2BQ4=
 github.com/magiconair/properties v1.8.1/go.mod h1:PppfXfuXeibc/6YijjN8zIbojt8czPbwD3XqdrwzmxQ=
 github.com/mailru/easyjson v0.0.0-20160728113105-d5b7844b561a/go.mod h1:C1wdFJiN94OJF2b5HbByQZoLdCWB1Yqtg26g4irojpc=