[tt] misinterprets the relative path to the templates folder

[dkasimovskiy]

Steps to reproduce:

1. Init tt in the folder inside your home directory (cd /home/d/git && tt init)
2. Set relative path to the templates folder in the /home/d/git/tt.yaml (~/git/repo/templates/tt)
3. Try to create new app with template (tt create tdg --name tt_tdg_app)
4. Got error template 'tdg' is not found

d@m1book8715:~/git$ tt cfg dump
/home/d/git/tt.yaml:
tt:
  modules:
    directory: /home/d/git/modules
  app:
    run_dir: /home/d/git/var/run
    log_dir: /home/d/git/var/log
    log_maxsize: 100
    log_maxage: 8
    log_maxbackups: 10
    restart_on_failure: false
    wal_dir: /home/d/git/var/lib
    memtx_dir: /home/d/git/var/lib
    vinyl_dir: /home/d/git/var/lib
    bin_dir: /home/d/git/bin
    inc_dir: /home/d/git/include
    instances_enabled: /home/d/git/instances.enabled
    tarantoolctl_layout: false
  ee:
    credential_path: ""
  templates:
  - path: /home/d/git/~/git/repo/templates/tt
  repo:
    rocks: ""
    distfiles: /home/d/git/distfiles

Expected behavior:

• Relative paths works correctly