Add SSL support to mysqldump.

[cdrake]

Added underpinnings to retrieve SSL certs from remote machine via SCP. SSL cert changes are in compute.py and mysql_util.py. Also improved support for Service Accounts.

[codecov[bot]]

Codecov Report

Merging #228 into dev will increase coverage by 4.71%. The diff coverage is n/a.

@@             Coverage Diff              @@
##                dev     #228      +/-   ##
============================================
+ Coverage     78.25%   82.97%   +4.71%     
+ Complexity      547      203     -344     
============================================
  Files            68       34      -34     
  Lines          4360     1104    -3256     
  Branches        332       66     -266     
============================================
- Hits           3412      916    -2496     
+ Misses          848      179     -669     
+ Partials        100        9      -91

Impacted Files	Coverage Δ	Complexity Δ
.../cloud/pontem/BaseCloudSpannerDatabaseRestore.java
.../cloud/pontem/AvroCloudSpannerDatabaseRestore.java
...loud/pontem/FormatStructAsGenericRecordFnTest.java
...oud/pontem/AvroCloudSpannerDatabaseBackupTest.java
...ntem/CloudSpannerDatabaseBackupIntegrityCheck.java
...tem/FormatSpannerTablesListStructAsTextFnTest.java
...java/com/google/cloud/pontem/TableInformation.java
...CloudSpannerDatabaseRestoreIntegrityCheckTest.java
...rc/test/java/com/google/cloud/pontem/UtilTest.java
...e/cloud/pontem/BaseCloudSpannerDatabaseBackup.java
... and 24 more

[codecov[bot]]

Codecov Report

Merging #228 into dev will increase coverage by 4.71%. The diff coverage is n/a.

@@             Coverage Diff              @@
##                dev     #228      +/-   ##
============================================
+ Coverage     78.25%   82.97%   +4.71%     
+ Complexity      547      203     -344     
============================================
  Files            68       34      -34     
  Lines          4360     1104    -3256     
  Branches        332       66     -266     
============================================
- Hits           3412      916    -2496     
+ Misses          848      179     -669     
+ Partials        100        9      -91

Impacted Files	Coverage Δ	Complexity Δ
.../cloud/pontem/BaseCloudSpannerDatabaseRestore.java
.../cloud/pontem/AvroCloudSpannerDatabaseRestore.java
...loud/pontem/FormatStructAsGenericRecordFnTest.java
...oud/pontem/AvroCloudSpannerDatabaseBackupTest.java
...ntem/CloudSpannerDatabaseBackupIntegrityCheck.java
...tem/FormatSpannerTablesListStructAsTextFnTest.java
...java/com/google/cloud/pontem/TableInformation.java
...CloudSpannerDatabaseRestoreIntegrityCheckTest.java
...rc/test/java/com/google/cloud/pontem/UtilTest.java
...e/cloud/pontem/BaseCloudSpannerDatabaseBackup.java
... and 24 more