[SPARK-21223] Change fileToAppInfo in FsHistoryProvider to fix concurrent issue.

# What issue does this PR address ?
Jira:https://issues.apache.org/jira/browse/SPARK-21223
fix the Thread-safety issue in FsHistoryProvider
Currently, Spark HistoryServer use a HashMap named fileToAppInfo in class FsHistoryProvider to store the map of eventlog path and attemptInfo.
When use ThreadPool to Replay the log files in the list and merge the list of old applications with new ones, multi thread may update fileToAppInfo at the same time, which may cause Thread-safety issues, such as  falling into an infinite loop because of calling resize func of the hashtable.

Author: 曾林西 <zenglinxi@meituan.com>

Closes #18430 from zenglinxi0615/master.