fix(RemoteFrappeSite): Make method more robust

[cogk]

What if your site is api-xyz.example.com 😄?

https://api-xyz.example.com/api/method/frappe.ping is not correctly split because /api appears twice

[codecov]

Codecov Report

Attention: Patch coverage is 0% with 1 line in your changes missing coverage. Please review.

Project coverage is 42.19%. Comparing base (58bd325) to head (16eb010).

Files with missing lines	Patch %	Lines
press/utils/__init__.py	0.00%	1 Missing ⚠️

Additional details and impacted files

@@           Coverage Diff           @@
##           master    #2318   +/-   ##
=======================================
  Coverage   42.19%   42.19%           
=======================================
  Files         376      376           
  Lines       28695    28695           
=======================================
  Hits        12109    12109           
  Misses      16586    16586           

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