Preserve programmatically set context config locations
Prior to this fix, ContextLoader(Listener)'s would overwrite any
value set directly against a WebApplicationContext's #setConfigLocation
method. This is a likely scenario when using Spring 3.1's new
WebApplicationInitializer support.
Now a check is performed to ensure that the ContextLoader init-param
value is non-null before doing the overwriting.
Added tests to ensure that all expected precedence, overwriting and
defaulting of context config locations works as expected.
Issue:
SPR-8510