init: lock blocksdir in addition to datadir

This guards against 2 processes running with separate datadirs but the same
blocksdir.

It's not likely to happen currently, but may be more relevant in the future
with applications using the kernel.

Note that the kernel does not currently do any dir locking, but it should.

Author: theuni

src/init.cpp

@@ -1086,7 +1086,8 @@ static bool LockDirectory(const fs::path& dir, bool probeOnly)
 }
 static bool LockDirectories(bool probeOnly)
 {
-    return LockDirectory(gArgs.GetDataDirNet(), probeOnly);
+    return LockDirectory(gArgs.GetDataDirNet(), probeOnly) && \
+           LockDirectory(gArgs.GetBlocksDirPath(), probeOnly);
 }
 
 bool AppInitSanityChecks(const kernel::Context& kernel)