component/replication-manager: pin golang to 1.16

when using golang 1.17 build fail with errors like:

    github.com/jacobsa/fuse/internal/buffer.memclr: relocation target runtime.memclrNoHeapPointers not defined for ABI0 (but is defined for ABIInternal)

software/repman/software.cfg

@@ -33,6 +33,10 @@ parts =
 [python]
 part = python3
 
+[gowork]
+# replication-manager does not build on golang 1.17
+golang = ${golang1.16:location}
+
 [instance.cfg]
 recipe = slapos.recipe.template:jinja2
 rendered = ${buildout:directory}/instance.cfg