Double history size when switch back and forth

[tmpm697]

default enter local history then switch to global or switch back and forth local and global, I observe when presenting via fzf, the size of history that actually double / tripple.

for e.g: I have history size 4k, if I switch back and forth and use fzf to surf history buffer then, the line of the same command in history 4k will be doubled / trippled to 8k / 12k. This actually doesn't mess the history file but I guess for consistencies, when a terminal is in global and its history size is 4k then when open new another terminal it display 8k because it trying to lock somehow on history file but can not.

@jimhester