Change bits_::m_bits to a vector

Although the order doesn't matter, making this into a vector makes sense
for the parser - Spirit parses stuff in some order, so a vector is
necessary.

Change-Id: I2ee75f02908911eb28d16c898401f0620afd4208
diff --git a/src/sysrepo_access.cpp b/src/sysrepo_access.cpp
index 6357a7a..6176f67 100644
--- a/src/sysrepo_access.cpp
+++ b/src/sysrepo_access.cpp
@@ -68,7 +68,7 @@
         while (!ss.eof()) {
             std::string bit;
             ss >> bit;
-            res.m_bits.insert(bit);
+            res.m_bits.push_back(bit);
         }
         return res;