OSGi: enable root-context tests

[denis-anisimov]

#4416 as a fix for #4227 adds IT tests for OSGi.
There are a number of failing tests which are disable via category IgnoreOSGi.
All tests should be fixed at some point and enabled in the end.

All tests may be divided into several categories:

• template related tests. Templates requires polymer webjar. Webjars don't work because of Webjars are not OSGi compatible #4413.
• push related tests. Currently they don't work because Jetty server in Felix is not properly configured for Push. Push should be configured and tests should be enabled.
• other tests which fails. The reason should be investigated. Issues should be fixed and tests should be enabled.

I will create a ticket for every category.

[mcollovati]

Compatibility mode support, that is required by OSGi add-on, is not supported anymore.