deb#749592 mysql-connector doesn't work with remote connections

and also
fdo#77584 mysql-connector doesn't work over SSH tunnel

Not sure exactly how this got broken, I suspect that the UI code
has started unconditionally passing down the properties, just filling
them with empty spaces for the unused ones.

Anyhow, this appears to fix the problem.

Change-Id: I7ac2a0d6bae610f47d2a28daa9beb3ef0e2dbb52
Reviewed-on: https://gerrit.libreoffice.org/9565Reviewed-by: Caolán McNamara <caolanm@redhat.com>
Tested-by: Caolán McNamara <caolanm@redhat.com>

mysqlc/source/mysqlc_connection.cxx

@@ -158,10 +158,10 @@ void OConnection::construct(const OUString& url, const Sequence< PropertyValue >
             OSL_VERIFY( pIter->Value >>= aPass );
         } else if (pIter->Name.equalsAscii("LocalSocket")) {
             OSL_VERIFY( pIter->Value >>= sUnixSocket );
-            unixSocketPassed = true;
+            unixSocketPassed = !sUnixSocket.isEmpty();
         } else if (pIter->Name.equalsAscii("NamedPipe")) {
             OSL_VERIFY( pIter->Value >>= sNamedPipe );
-            namedPipePassed = true;
+            namedPipePassed = !sNamedPipe.isEmpty();
         } else if ( pIter->Name.equalsAscii("PublicConnectionURL")) {
             OSL_VERIFY( pIter->Value >>= m_settings.connectionURL );
         } else if ( pIter->Name.equalsAscii("NewURL")) {    // legacy name for "PublicConnectionURL"