Grok pattern search bar on pattern list page affects search bar on Create Pattern modal

The value entered in the search bar on the list of Grok patterns filters the available patterns when creating a new pattern.

## Expected Behavior

The value entered in the search bar on the list of Grok patterns does not affect the search bar in the Create Pattern modal.

## Current Behavior

The value entered in the search bar on the list of Grok patterns affects the search bar in the Create Pattern modal.

## Possible Solution

Use separate variables for the two search bar values

## Steps to Reproduce (for bugs)

1. Go to System - Grok Patterns
2. Type "greedy" which will give one result GREEDYDATA
3. Go to Create pattern
4. In filter pattern only GREEDYDATA will show up and no other search will work
## Context

https://github.com/Graylog2/support/issues/90
## Your Environment

* Graylog Version: 6.0.5