Combine common keywords and fix argument issue

Combine common keywords and fix argument issue

https://git.opendaylight.org/gerrit/c/integration/test/+/88446
broke the getsingle.robot suite because it was duplicating some
work that should be common. So combined the duplication between
it and max_devices in to the netconfkeywords lib. getmulti.robot
is also sharing keywords now.

Also add back 300s timeout for Wait_Connected keyword that was
migrated to NetconfKeywords.robot lib in parallel with the
review/merge of https://git.opendaylight.org/gerrit/c/integration/test/+/88662

Signed-off-by: Jamo Luhrsen <jluhrsen@gmail.com>
Change-Id: I063b6e13cdbafff778186043a2250da284365091
Signed-off-by: Jamo Luhrsen <jluhrsen@gmail.com>