@Mock fails if domain class has property named 'list'

Following exception is thrown if we try to mock domain with property named 'list' if constraint is defined for it. Changing property name resolves issue. There is single domain and unit spec for it in project under: https://github.com/droggo/bugs/tree/master/DomainPropertyNameListBug

Appeared after migrating to grails 2.5.2 from 2.4.2

```
class DomainWithListPropertyName {

String list

static constraints = {
list nullable: true
}
}
```

```
@Mock(DomainWithListPropertyName)
class DomainWithListPropertyNameSpec extends Specification {
void 'ensure domain may be saved'(){
expect:
new DomainWithListPropertyName().save(failOnError: true)
}
}
```

```
ensure domain may be saved(grails.DomainWithListPropertyNameSpec)
|
java.lang.IllegalStateException: Method on class [grails.DomainWithListPropertyName] was used outside of a Grails application. If running in the context of a test using the mocking API or bootstrap Grails correctly.
at grails.DomainWithListPropertyName._clinit__closure1(DomainWithListPropertyName.groovy:12)
at org.grails.datastore.mapping.config.groovy.MappingConfigurationBuilder.evaluate(MappingConfigurationBuilder.groovy:83)
at org.grails.datastore.mapping.config.AbstractGormMappingFactory.createMappedForm(AbstractGormMappingFactory.java:63)
at org.grails.datastore.mapping.keyvalue.mapping.config.GormKeyValueMappingFactory.createMappedForm(GormKeyValueMappingFactory.java:39)
at org.grails.datastore.mapping.keyvalue.mapping.config.GormKeyValueMappingFactory.createMappedForm(GormKeyValueMappingFactory.java:28)
at org.grails.datastore.mapping.keyvalue.mapping.config.KeyValuePersistentEntity.(KeyValuePersistentEntity.java:35)
at org.grails.datastore.mapping.keyvalue.mapping.config.KeyValueMappingContext.createPersistentEntity(KeyValueMappingContext.java:95)
at org.grails.datastore.mapping.model.AbstractMappingContext.addPersistentEntities(AbstractMappingContext.java:174)
at grails.test.mixin.domain.DomainClassUnitTestMixin.mockDomains(DomainClassUnitTestMixin.groovy:86)
at org.spockframework.util.ReflectionUtil.invokeMethod(ReflectionUtil.java:153)
at org.spockframework.runtime.model.MethodInfo.invoke(MethodInfo.java:84)
at org.spockframework.runtime.extension.MethodInvocation.proceed(MethodInvocation.java:88)
at org.spockframework.runtime.extension.builtin.AbstractRuleInterceptor$1.evaluate(AbstractRuleInterceptor.java:37)
at grails.test.runtime.TestRuntimeJunitAdapter$1$2.evaluate(TestRuntimeJunitAdapter.groovy:49)
at org.spockframework.runtime.extension.builtin.TestRuleInterceptor.intercept(TestRuleInterceptor.java:38)
at org.spockframework.runtime.extension.MethodInvocation.proceed(MethodInvocation.java:87)
at org.spockframework.runtime.extension.MethodInvocation.proceed(MethodInvocation.java:88)
at org.spockframework.runtime.extension.builtin.AbstractRuleInterceptor$1.evaluate(AbstractRuleInterceptor.java:37)
at grails.test.runtime.TestRuntimeJunitAdapter$3$4.evaluate(TestRuntimeJunitAdapter.groovy:76)
at org.spockframework.runtime.extension.builtin.ClassRuleInterceptor.intercept(ClassRuleInterceptor.java:38)
at org.spockframework.runtime.extension.MethodInvocation.proceed(MethodInvocation.java:87)
```

Start with the DomainPropertyNameListBug reproduction linked in the issue and the DomainClassUnitTestMixin.groovy stack-frame location. Trace how the list constraint is processed through the mapping configuration during @Mock setup. Done means the provided domain unit spec saves successfully without the IllegalStateException, with a regression test covering the list property and nullable constraint.

Written by the indexing model from the issue text.