playground: Update many variable names for *Calls to call.

In a previous change I renamed many types from *Context to *Call.
In this change I am trying to also update as many variable names
as can easily be changed.  I have only altered variables whose
type was trivially determined.

MultiPart: 6/8

Change-Id: I41760101d0472440b63d39df9833ba97d30274f6
1 file changed
tree: 4a28eacebb7d14be0331fb4f348773d57d53f302
  1. client/
  2. go/
  3. pgbundle/
  4. .gitignore