Escaping special characters doesn't work correctly in issue search

Summary

Escaping special characters doesn't work correctly in issue search. It seems they are ignored.

Steps to Reproduce

1. Create an issue whose summary is 'fifteen'
2. Create an issue whose summary is 'fifteen*'
3. Search the second issue with a following keyword

   "fifteen\\*"

Expected Results

Hits only the second issue. (The one which has a summary 'fifteen*')

Actual Results

Hits both of the issues.

Notes

According to JRA-25092,

summary ~ "fifteen\\*" (works)

but it doesn't look working.

Actually the same behavior is also applied to special characters used in the beginning of the word. If we also create an issue with the summary is '*fifteen' if we search for

summary ~ "\\*fifteen"

this search will return all three issues (with summary 'fifteen', '*fifteen' and 'fifteen*').