Use SolarMutexGuard instead of pairs of Acquire/ReleaseSolarMutex

Change-Id: I7ff41dd932fd9860dff944b3bf8ff5bdc230ae5d
Make common paths member variables.

We'll need these for other tests too.

Change-Id: Ia99c2e60f5e5bb24a83875a9dcf85a6b4f54beb4
Use one test instance to run all LOK tests.

Recreating Office instances after destruction (when still
within the same process) currently fails, hence we need
to do all tests at once for now.

Change-Id: Ic7652c909e1cd970fe1ee76995e61fb6aae8f96c
LOK: add slide name retrieval test.

Change-Id: I6d2bc4dfa634223da662af6f7c9a91f06cfe7534
LOK: add test for getDocumentType.

Change-Id: I264567f73dae9ecd061e09c4413857f793fcac48
LOK documentLoad needs SolarMutex protection too.

We probably need to do this for most of LOK now that
we use soffice_main.

Change-Id: I77be7865511c083679cf2f68b0e5df106506fd70
LOK: add document loading failure test.

We don't really have any way of telling the client that the file didn't
exist yet though, so not very useful so far.

Change-Id: I1db386781b88b345f3e9cb4f37838ca1d95f92f9