tdf#101094 (27): Add a mutex guard to OPTIONS neon dispatch calls

This is a sort of follow up to commit:
510da291:

"forced to make certain neon api calls thread-safe due to cups

rhbz#637738 libgcrypt that's been initialized already by cups to be
non-threadsafe is therefore then also non-threadsafe. neon uses
libgcrypt. So in the (as this is the usual circumstance) case that
cups is initialized before neon, then libgcrypt is not threadsafe
even though neon attempt to initialize it as such."

Change-Id: I1f868642ac15bf9fa25d3edd46390467d8fce1f5
Reviewed-on: https://gerrit.libreoffice.org/28401Tested-by: Jenkins <ci@libreoffice.org>
Reviewed-by: Giuseppe Castagno <giuseppe.castagno@acca-esse.eu>

ucb/source/ucp/webdav-neon/NeonSession.cxx

@@ -845,18 +845,19 @@ void NeonSession::OPTIONS( const OUString & inPath,
                            const DAVRequestEnvironment & rEnv )
     throw( std::exception )
 {
-
-    osl::Guard< osl::Mutex > theGuard( m_aMutex );
     SAL_INFO( "ucb.ucp.webdav", "OPTIONS - relative URL <" << inPath << ">" );
 
     rOptions.reset();
 
     Init( rEnv );
+    int theRetVal;
 
     ne_request *req = ne_request_create(m_pHttpSession, "OPTIONS", OUStringToOString(
                                             inPath, RTL_TEXTENCODING_UTF8 ).getStr());
-
-    int theRetVal = ne_request_dispatch(req);
+    {
+        osl::Guard< osl::Mutex > theGlobalGuard( aGlobalNeonMutex );
+        theRetVal = ne_request_dispatch(req);
+    }
 
     //check if http error is in the 200 class (no error)
     if (theRetVal == NE_OK && ne_get_status(req)->klass != 2) {