pcbnew: Can't drag a via in 45 degree mode

Description

Via can not be dragged in pcbnew via 'D' keyboard shortcut (45 degree angle mode).

Steps to reproduce

1. Hover mouse pointer over a via. This can be either via on a track or via in a zone.
2. Press 'D' to start dragging it
3. Position via to a different place and click the mouse - via springs back to its previous place, all changes to tracks are reverted back.

KiCad Version

Application: Pcbnew

Version: 5.99.0-unknown-0103164~89~ubuntu20.04.1, release build

Libraries:
	wxWidgets 3.0.4
	libcurl/7.68.0 OpenSSL/1.1.1f zlib/1.2.11 brotli/1.0.7 libidn2/2.2.0 libpsl/0.21.0 (+libidn2/2.2.0) libssh/0.9.3/openssl/zlib nghttp2/1.40.0 librtmp/2.3

Platform: Linux 5.4.0-42-generic x86_64, 64 bit, Little endian, wxGTK

Build Info:
	Date: Jul 27 2020 15:19:14
	wxWidgets: 3.0.4 (wchar_t,wx containers,compatible with 2.8) GTK+ 3.24
	Boost: 1.71.0
	OCE: 6.9.1
	Curl: 7.68.0
	ngspice: 31
	Compiler: GCC 9.3.0 with C++ ABI 1013

Build settings:
	KICAD_SCRIPTING=ON
	KICAD_SCRIPTING_MODULES=ON
	KICAD_SCRIPTING_PYTHON3=ON
	KICAD_SCRIPTING_WXPYTHON=ON
	KICAD_SCRIPTING_WXPYTHON_PHOENIX=ON
	KICAD_SCRIPTING_ACTION_MENU=ON
	BUILD_GITHUB_PLUGIN=ON
	KICAD_USE_OCE=ON
	KICAD_SPICE=ON