[mem][solaris] improve prtconf memory size scraping

Accept uppercase Memory, that's how it appears to be at least in Solaris
11.3 and OpenIndiana oi_151a7.

mem/mem_solaris.go

@@ -67,7 +67,7 @@ func zoneName() (string, error) {
 	return strings.TrimSpace(string(out)), nil
 }
 
-var globalZoneMemoryCapacityMatch = regexp.MustCompile(`memory size: ([\d]+) Megabytes`)
+var globalZoneMemoryCapacityMatch = regexp.MustCompile(`[Mm]emory size: ([\d]+) Megabytes`)
 
 func globalZoneMemoryCapacity() (uint64, error) {
 	prtconf, err := exec.LookPath("prtconf")

v3/mem/mem_solaris.go

@@ -67,7 +67,7 @@ func zoneName() (string, error) {
 	return strings.TrimSpace(string(out)), nil
 }
 
-var globalZoneMemoryCapacityMatch = regexp.MustCompile(`memory size: ([\d]+) Megabytes`)
+var globalZoneMemoryCapacityMatch = regexp.MustCompile(`[Mm]emory size: ([\d]+) Megabytes`)
 
 func globalZoneMemoryCapacity() (uint64, error) {
 	prtconf, err := exec.LookPath("prtconf")