<C-u>, <C-p> and <C-n> mappings do not work in Vim >= v8.1.2194

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fzf version: dceb5d09cdb0d3158a3f79e59eb3c16ffe242d6b
fzf.vim version: bce6588d2422df75ca0091edac48aa9f87f163e5
Vim version:

```
VIM - Vi IMproved 8.1 (2018 May 18, compiled Nov 8 2019 16:14:53)
Included patches: 1-2269
Compiled by myitcv@myitcv
Huge version with GTK2 GUI. Features included (+) or not (-):
+acl -farsi -mouse_sysmouse -tag_any_white
+arabic +file_in_path +mouse_urxvt -tcl
+autocmd +find_in_path +mouse_xterm +termguicolors
+autochdir +float +multi_byte +terminal
-autoservername +folding +multi_lang +terminfo
+balloon_eval -footer -mzscheme +termresponse
+balloon_eval_term +fork() -netbeans_intg +textobjects
+browse +gettext +num64 +textprop
++builtin_terms -hangul_input +packages +timers
+byte_offset +iconv +path_extra +title
+channel +insert_expand -perl +toolbar
+cindent +job +persistent_undo +user_commands
+clientserver +jumplist +postscript +vartabs
+clipboard +keymap +printer +vertsplit
+cmdline_compl +lambda +profile +virtualedit
+cmdline_hist +langmap +python +visual
+cmdline_info +libcall -python3 +visualextra
+comments +linebreak +quickfix +viminfo
+conceal +lispindent +reltime +vreplace
+cryptv +listcmds +rightleft +wildignore
+cscope +localmap -ruby +wildmenu
+cursorbind +lua +scrollbind +windows
+cursorshape +menu +signs +writebackup
+dialog_con_gui +mksession +smartindent +X11
+diff +modify_fname -sound -xfontset
+digraphs +mouse +spell +xim
+dnd +mouseshape +startuptime +xpm
-ebcdic +mouse_dec +statusline +xsmp_interact
+emacs_tags -mouse_gpm -sun_workshop +xterm_clipboard
+eval -mouse_jsbterm +syntax -xterm_save
+ex_extra +mouse_netterm +tag_binary
+extra_search +mouse_sgr -tag_old_static
system vimrc file: "$VIM/vimrc"
user vimrc file: "$HOME/.vimrc"
2nd user vimrc file: "~/.vim/vimrc"
user exrc file: "$HOME/.exrc"
system gvimrc file: "$VIM/gvimrc"
user gvimrc file: "$HOME/.gvimrc"
2nd user gvimrc file: "~/.vim/gvimrc"
defaults file: "$VIMRUNTIME/defaults.vim"
system menu file: "$VIMRUNTIME/menu.vim"
fall-back for $VIM: "/home/myitcv/usr/vim/share/vim"
Compilation: gcc -c -I. -Iproto -DHAVE_CONFIG_H -DFEAT_GUI_GTK -pthread -I/usr/include/gtk-2.0 -I/usr/lib/x86_64-linux-gnu/gtk-2.0/include -I/usr/include/gio-unix-2.0 -I/usr/include/cairo -I/usr/include/pango-1.0 -I/usr/include/atk-1.0 -I/usr/include/cairo -I/usr/include/pixman-1 -I/usr/include/gdk-pixbuf-2.0 -I/usr/include/libmount -I/usr/include/blkid -I/usr/include/pango-1.0 -I/usr/include/harfbuzz -I/usr/include/pango-1.0 -I/usr/include/fribidi -I/usr/include/glib-2.0 -I/usr/lib/x86_64-linux-gnu/glib-2.0/include -I/usr/include/uuid -I/usr/include/freetype2 -I/usr/include/libpng16 -g -O2 -U_FORTIFY_SOURCE -D_FORTIFY_SOURCE=1
Linking: gcc -L/usr/local/lib -Wl,--as-needed -o vim -lgtk-x11-2.0 -lgdk-x11-2.0 -lpangocairo-1.0 -latk-1.0 -lcairo -lgdk_pixbuf-2.0 -lgio-2.0 -lpangoft2-1.0 -lpango-1.0 -lgobject-2.0 -lglib-2.0 -lfontconfig -lfreetype -lSM -lICE -lXpm -lXt -lX11 -lXdmcp -lSM -lICE -lm -ltinfo -lnsl -ldl -L/usr/lib/x86_64-linux-gnu -lluajit-5.1 -L/home/myitcv/.pythons/2.7.15/lib/python2.7/config -lpython2.7 -lpthread -ldl -lutil -lm -Xlinker -export-dynamic
```

Per https://groups.google.com/d/msg/vim_dev/d0gi0UT3bfw/aGMspiODAwAJ I'm seeing some issues using fzf with Vim version `v8.1.2194` and later.

Specifically I'm seeing issues using , and within fzf. I get control sequences printed to the screen instead of the clearing the line, previous and next elements respectively.

The only setup that works for me is to disable this feature via:

let &t_TI = ""
let &t_TE = ""

Creating this issue here in order to get your expertise whilst investigating (because I can't honestly say I know much about what fzf is doing here)

cc @brammool