Contacts: fix wrong background color on contact detail fragment on landscape

Google hardcoded white color in the landscape view. Normal portrait view
uses f5f5f5. Redirect whe color to colors.xml so it uses the default color
background_primary.

This fixes as well the issue that on dark mode enabled (manually/sensor/daytime)
the background remained white.

Change-Id: Id7915bb19bbe87909eecb39646755e0bc130b287